What's the name of the fallacy here?

A criticizes Israel for something unrelated to Judaism.
B says A is anti-Semitic.

I have a sense of what you mean but I think the first sentence is problematic. The issue is not whether it is related to Judaism or not. For example, one could criticize Israel for making everyone perform Jewish rituals. This has to do with Judaism, but it is not anti-semitic to criticize it.

In any case it is kind of red herring. A relevence fallacy.

But it is also a kind of mind reading ad hom. The real reason you dislike this is because it is a jewish state. IOW one does not focus on the criticized policy but on the motivations for criticizing the policy. Hence it’s to the man.

Unfortunately this is sometimes the case, but you still have to defend the merits of the policy and its consequences, even if some of the critics are anti-semitic or in other arguments have some other motive.

I was veering towards fallacy of composition. Some Israelis are Jews, but that doesn’t make Israel and everything it does ‘Jewish’. I’m not convinced that’s the right fallacy here, though.

I’m not wholly convinced that it’s an ad hominem either, because much as I find anti-Semitism distasteful, holding anti-Semitic opinions has no bearing on one’s ability to produce a sound argument. At best, the charge of anti-Semitism implies bias, which implies the possibility of not formulating a sound argument. EDIT: I read that an ad hominem can indeed merely imply bias.

But it does seem to be some kind of fallacy of relevance. Which becomes clear with a similar but even more obviously fallacious example:

A: ‘Yemen should not have been awarded the World Cup because of the corruption involved.’
B: ‘You’re Islamophobic.’

which is what makes it ad hom.(you may be agreeing with me here,but it seemed to be disagreeing) Someone criticizes some specific action the Israeli military does in Gaza. They describe the action, perhaps with focus on civilian deaths, whatever.

if you say this is anti-semitism, you are 1) saying you know the real motives of the person making the argument (so it is a psychic claim) and 2) you are not countering the argument.

You went for the man, not the argument. You could challenge the other person about why they do not make the same attack on Palestian behavior, or US behavior or whatever, but if you do this you must still defend the actions. You can point out the bias, but this does not excuse the action in Gaza. Only a defense of that will do that.

Right, which you then need to show. It would be fine to point out why the judgment is not correct, then go ad hom and say the person making the charge only applies in his judgments to Israel. Then you could say they have an anti-israel bias. This need not necessarily be anti-semitism.

The problem is, many lib-tards will hit the block button before you even make it to the fallacy discussion stage.

This is the problem with full social mental retardation.

Not saying im a trump supporter, i aint a trump supporter.

But if trump says MS13 gang are animals, the liberals say it is a whitemale conspiracy against the mexicans and that trump is saying all mexicans are animals.

Not sure logic or reason is a high prority in the modern mind.

Personally, I consider myself in many ways, a liberal, or rebel. But I am not in the sense of, the modern liberal, the lib-tard.