Hero Worship Is Bad
It should be obvious to anyone that taking the words of anyone, including someone you like (or even specially someone you like) without skepticism is a dangerous path. For example, you may like Gandhi's philosophy of non-violence, or admire him for whatever reason.
That is hardly an excuse to take anything he said as worth much, specially when it's about subjects he had absolutely no idea about, because he had a tendency to be absolutely sure he knew everything about everything.
For example, did you know he wrote a book about health? Here's a quote from it:
One question which I have asked myself again and again, in the course of writing this book, is why I of all persons should write it. Is there any justification at all for one like me, who am no doctor, and whose knowledge of the matters dealt with in these pages must be necessarily imperfect, attempting to write a book of this kind?
My defence is this. The “science” of medicine is itself based upon imperfect knowledge, most of it being mere quackery. But this book, at any rate, has been prompted by the purest of motives. The attempt is here made not so much to show how to cure diseases as to point out the means of preventing them. And a little reflection will show that the prevention of disease is a comparatively simple matter, not requiring much specialist knowledge, although it is by no means an easy thing to put these principles into practice. Our object has been to show the unity of origin and treatment of all diseases, so that all people may learn to treat their diseases themselves when they do arise, as they often do, in spite of great care in the observance of the laws of health.
Do you notice the bait and switch? He knows little about the matter, but he will write the book anyway because it's really about the simple subject of disease prevention. But reading it "all people may learn how to treat diseases themselves". And not just a few diseases but all diseases. That paragraph reeks of false modesty and simple dishonesty.
But hey, did you know that he could cure the plague?
I have tried this single treatment [a mud poultice] for all varieties from simple fever up to Bubonic Plague, with invariably satisfactory results.
Of course, in the next sentence it says:
In 1904, there was a severe outbreak of plague among the Indians in South Africa. It was so severe that, out of 23 persons that were affected, as many as 21 died within the space of 24 hours; and of the remaining two, who were removed to the hospital, only one survived, and that one was the man to whom was applied the mud-poultice.
I wonder what is a result less than satisfactory.
There are obvious misunderstandings of basic facts, such as how respiration works  what the stomach does  and even how many bones there are in a human chest, and there are, of course, things that are just weird:
Cocoa is fully as harmful as coffee, and it contains a poison which deadens the perceptions of the skin.
Even habitual coffee-drinkers will be unable to perceive any difference in taste between coffee and this substitute. Good and well-sifted wheat is put into a frying-pan over the fire and well fried, until it has turned completely red, and begun to grow dark in colour. Then it is powdered just like coffee. A spoon of the powder is then put into a cup, and boiling water poured on to it. Preferably keep the thing over the fire for a minute, and add milk and sugar, if necessary, and you get a delicious drink, which is much cheaper and healthier than coffee. Those who want to save themselves the trouble of preparing this powder may get their supply from the Satyagraha Ashram, Ahmedabad.
The first class, which is the largest, consists of those who, whether by preference or out of necessity, live on an exclusive vegetable diet. Under this division come the best part of India, a large portion of Europe, and China and Japan. The staple diet of the Italians is macaroni, of the Irish potato, of the Scotch oatmeal, and of the Chinese and Japanese rice. 
Wheat is the best of all the cereals. Man can live on wheat alone, for in it we have in due proportion all the elements of nutrition. Many kinds of edibles can be made of wheat, and they can all be easily digested.  [...] man can retain his strength by living on mere wheat boiled in water.
And finally, there are the bits which are not just wrong, but also absolutely fucking dangerous.
Did you know he says smallpox is not contagious, and is really a digestive tract condition?
[Smallpox] is caused, just like other diseases, by the blood getting impure owing to some disorder of the bowels; and the poison that accumulates in the system is expelled in the form of small-pox. If this view is correct, then there is absolutely no need to be afraid of small-pox. If it were really a contagious disease, everyone should catch it by merely touching the patient; but this is not always the case. [...] This has given rise to the superstition that it is a contagious disease, and hence to the attempt to mislead the people into the belief that vaccination is an effective means of preventing it.
Oh, vaccination! You see, this book was published in 1921. By 1921, smallpox was already disappearing in Europe because vaccionation worked. And smallpox vaccination had worked for decades. He either knew nothing about how effective it was, or did not care.
I think the problem here is, unsurprisingly, that to someone with Gandhi's background vaccination was evil and just couldn't be accepted as something positive.
Vaccination is a barbarous practice, and it is one of the most fatal of all the delusions current in our time, not to be found even among the so-called savage races of the world.
Moreover, vaccination is a very dirty process, for the serum which is introduced into the human body includes not only that of the cow, but also of the actual small-pox patient. An average man would even vomit at the mere sight of this stuff. If the hand happens to touch it, it is always washed with soap. The mere suggestion of tasting it fills us with indignation and disgust. But how few of those who get themselves vaccinated realise that they are in effect eating this filthy stuff!
As has been well said, cowards die a living death, and our craze for vaccination is solely due to the fear of death or disfigurement by small-pox. 
I cannot also help feeling that vaccination is a violation of the dictates of religion and morality. The drinking of the blood of even dead animals is looked upon with horror even by habitual meat-eaters. Yet, what is vaccination but the taking in of the poisoned blood of an innocent living animal? Better far were it for God-fearing men that they should a thousand times become the victims of small-pox and even die a terrible death than that they should be guilty of such an act of sacrilege.
And there you have it, the classical moral arithmetic of the religious: it is better for your son to die in horrible suffering or be disfigured than for a drop of cow serum to be injected in him. How's that for non-violent?
Fuck that shit, Gandhi. Fuck that shit.