Once again, someone is wrong on the internet and deserves to be challenged!

Hmm, I think the literal translation is "and it is really needed to fight against this!"

I was also thinking "they need to be set straight!" How about that?

"С этим" doesn't mean "against those people", it means "against this [situation]" here.

Although perhaps there is no any good-sounding, more literal equivalent in English.

Ah, ok, so maybe something like "attack this issue?"

That sounds good!

Also don't forget about "безусловно".

Is it more like "definitely" or "certainly"?

"Once again, someone is wrong on the internet and the issue must definitely be attacked!"

It sounds kinda clumsy now >.<

Just "Once again, someone is wrong on the internet!" by itself sounds very sarcastic. Adding the rest sort of dumbs it down.

Wow! You are right. I've edited the Russian sentence.