A popular saying online is "The Internet is serious business".
Of course, the saying is so heavily sarcastic that even I'm not misled by it.
The Internet is a sounding board. But it's not the be all or end all. What people say online shouldn't have the power to affect you. If it's upsetting you that much, then it's likely that you need to address the issue of your own insecurities rather than lashing back out at people online who've offended you.
I find that the best way to deal with poor-taste jokes and misguided humor/insults is to shrug and laugh it off. If you respond with aggression or obvious upset, you give them exactly the reaction they crave and you fuel them to do it more.
Also, be sure that you're not misinterpreting them. Teasing is not always obvious in its intent. Sometimes it's intended as a friendly jibe rather than an attack.
I openly admit that I often have a difficulty in understanding if someone is genuinely insulting me or if they're just joking around. So I try to be careful and react in a way that covers both scenarios.
For example, an insult often thrown at Aspies is "Go back to your hugbox!". Of course, it's a rather patronizing and stereotypical view that all people with AS have a hugbox. I don't have one (although admittedly I would like one! Lying down under a mattress just doesn't work as well), but if someone said that to me I would just laugh and say "I can't, it's broken. Can I borrow yours?" or something playful along those lines.
Laughing and poking gentle fun of yourself if the best was to diffuse a direct confrontation. And if something upsets you that much online, the best thing to do is just click the little 'x' in the corner of your browser and leave the site
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~I wanna fly high, so I can reach the highest of all the heavens
Somebody will be waiting for me, so I've got to fly higher~