It would take two minutes to tweet:

I support Ukraine's defensive struggle against Russia but not fascist ideology. I was ignorant of the flag's significance, I apologise, & endeavour to do better. I'll be more careful in the future in how I represent this important cause.

It'd be basically meaningless bullshit, but it wouldn't leave people with the (likely correct) assumption that you uncritically and unwaveringly support neo-Nazis.