What is the fallacy “X is bad, Y is worse, therefore X is not bad” called?

I have often heard this type of argument: You are criticizing X using well-researched facts and arguments. Your interlocutor states that Y is much worse, with equally well-researched facts and arguments. Your interlocutor uses their argument that Y is worse to suggest that X is, in fact, good. X and Y are linked in a general sense: two alternative medicines (homeopathy & chiropractics). two politicians (May & Corbyn). two historical figures (Hitler & Stalin). This logical fallacy asserts that because Y is much worse than X, therefore X is good. What is this logical fallacy called? Clearly in a binary choice, the lesser evil should win: X is bad, Y is worse therefore you should chose X. ⚠ This is not what this question is about.⚠ Please re-read the last sentence. This logical fallacy asserts that because Y is much worse than X, therefore X would be a good thing. Not that it is a better choice, less-worst choice, the only choice but that it is a worthwhile choice on its own. In addition, there might not be just two choices or one might not even be asked to make a choice: the fact that Y is worst makes X good regardless of X's merits.