Whilst dealing with this kind of asshole in a work environment is a lot more complex, online they’re like dogs barking behind a wall - only doing it because they're aggressive simpletons and isolated from any problems from doing it - and just as unworthy of consideration or attention as one.

They really only have any impact on you when you give them more importance than they deserve.

Also keep in mind that these people are at the lower end of expertise and professionalism: top experts don't waste time with talking shit like that, they'll just either teach you or (most likely) ignore you because they think that stuff is too basic and not worth their time, and professionals are used to being professional and shit-talking ain't being professional - even in expertise terms these people are unimportant.