You brought up the example of the US in relation to WWII. If you make a comparison, you can’t get stroppy when people point out that it contradicts your main argument and in fact supports the argument that you’re trying to challenge.
However, for as long as you think the US is the Good Guy^TM^, you’re going to struggle to find examples that support your viewpoint, so you may want to be careful with any comparison. Otherwise, you’ll start to notice a pattern of them pointing out that the US was as monstrous as always in the cited example and then you’ll say they’re doing whataboutism ad infinitum.