"I have to suffer fools in real life..."
Yes, that's it. Everyone has so much stored-up aggression and the anonymous internet allows it expression.
Everyone feels what they feel, believes what they believe, etc. But we don't have to inflict it all on others. Being kind is not a humiliation, or a betrayal of what one really feels; it's just being kind. Don't we all need a little kindness? Today, it seems it's all about "I have a right" - people on trains or buses not giving their seat to old or infirm people because, as a 10-yr old boy I overheard on a train once said: I have a right to sit here. With my grey hair and walking stick, I have often been the only one on a crowded bus to give up my seat to older people.
I was taught to look out for people who needed my seat more than me. It's not about "right", it's about kindness and empathy.
A last thought: no-one can see your expression when you're typing your message and they can interpret what you write as aggressive, even when you were feeling sympathetic and sensible. I once put a message on my company's website, asking for a little empathy for those who had been made to retire or take an unwilling redundancy, and found a reply saying it was interesting that I was so angry about it - how can asking for empathy for others be interpreted as angry?
I'm sure that this post will also attract denunciations...