For instance, if Person A says:
The homeless are trash and should be treated as such
To which Person B responds
We should start to address the homeless problem by not dehumanizing them
What is the logical fallacy for Person A's response of
Unless you are willing to take them in, willing to sell all your possessions and bankrupt your family to provide for them, then you aren't doing anything to help.
I would classify this as a perfectionist fallacy, which is a variety of the false dilemma: Either you do things perfectly/completely, or else there is no point to doing any of it.
Now, for some things, a be-perfect-or-don't-do-it-at-all dilemma actually makes sense: building nuclear power plants comes to mind: yes, either you build then perfectly, or else it's probably a good idea not to build it at all.
But, when it comes to helping other people, doing something is still better than doing everything in your power. So, in those cases, the dilemma is a false dilemma.
I mean, we could see it as an enthymeme. One option to reconstruct an argument is:
(1) If you're not willing to take them in, willing to sell all your possessions and bankrupt your family to provide for homeless people then you're not helping them.
(2) If you're not helping then you don't act according to your claim as well.
(3) If you're not acting according to your claim as well then the claim is wrong.
(4) You're not willing to take them in, willing to sell all your possessions and bankrupt your family to provide for homeless people.
(C) Your claim is wrong.
I had to really bend it into shape to even address the claim of B. So if that's not what the person implied then they simply don't pose a relevant argument. It's possible that they just don't care about ethical claims at all and simply want to make B feel bad.
But if it is what they implied then we could demolish the argument at multiple points. Let's just grant premise 4. Premise 1 and 2 are factually wrong. But the main problem is premise 3. It's just not true whichever way we put it. I guess we could call it "whataboutism" or "tu quoque", but obviously we would have to explain to A that there's a premise which isn't even slightly plausible instead of just yelling fallacies.
edit: Oh yea, about the headline question. I guess such cases sound like "tu quoque". But it's not necessarily the case.
There may not be an argument here, hence no formal logical fallacy, but there is an informal fallacy, that of the false dilemma :
EITHER you treat the homeless as trash OR you are willing to take them in, willing to sell all your possessions and bankrupt your family to provide for them.
If you think think we should address the homeless problem by not dehumanizing the homeless, there are many ways of helping them short of the drastic option of selling all your possession and bankrupting your family by providing for them.
Social and political policies and programmes are possible. There can be community action. There are so many possibilities that the dilemma A presents you with is without credibility - unless A can rule out, by sound argument, all the possibilities short of the drastic option.
Unless you are willing to take them in, willing to sell all your possessions and bankrupt your family to provide for them, then you aren't doing anything to help.
I don't see a common fallacy here, but it is simply incorrect. The speaker is making the claim that the acts he named are the only acts which qualify as helping solve the problem of homelessness. He could mean this either in a practical sense, that all other acts do not have practical effect, or in a social sense, that all other acts are not seen by society as being helpful. Both of those claims are incorrect. Providing homes to the homeless has solved the problem of homelessness in several places. And society sees many acts outside of the short list he provided as helpful.
