That was without a doubt meant sarcastic.

Of course it was, thank you.

It's incredible that this needed to be explained.

As the sibling explained, it was sarcasm. It was satire of brain dead right wingers saying "stop making everything political" when political points apply, but then making things political politcal in stupid situations.

Example, someone shoots up a school, people say "if the Republican party hadn't obstructed gun legislation maybe this wouldn't have happened", they respond "StOp MaKiNg EvErYtHiNg PolItIcaL". But if the person is trans suddenly it's political.