That’s also probably why they call themselves “Strong Atheists.” As for me, I am an antitheist concerning some gods, I have no problem with the word when it is used correctly.
“I know there is no god” is in fact the antithesis of the theist position “I know god exists.” Whether it seems that way or not… these are true opposites. God either exists or it does not exist. There is no middle ground. Both propositions need to be supported with evidence. (Back to the jellybean analogy.) You can not tell me the number of jellybeans in the jar without counting them in some way. That is just a fact. And since you have no facts, I have nothing to believe.
Misnamed or not, it is the belief that no god exists (By definition.) If you use another definition we are not talking about the same thing.