Whataboutism is excusing your own faults by pointing out someone else's faults. Like when Democrats say "How can you support Roy Moore, he's a pedophile?" and Republicans say "Yeah, but what about Al Franken grabbing that woman's boobs?"
Well I mean, and I implore you not to misconstrue this as me being pro-Roy Moore, it actually is quite relevant that Al Franken also has a history of sexual misconduct. The controversy with Roy Moore is in large part a result of the two party system. The Democrats want to portray Republicans as having a sexual predator problem (which may or may not be true). It shows that the outrage may not be so earnest, and that it may have been blown out of proportion by the left since Al Franken isn't receiving as much pressure from them to step down as Roy Moore was.
I don't necessarily agree with this take, but I think it provides useful background information and changes the weight of each side's arguments. I think you should address the "whataboutism" rather than trying to silence it.
