Why do people fight online a lot?

I actually think that many of what we see as offense online is categorized as

1-people that had a bad day, exploding on strangers instead of taking it out closer

2-Miscommunication and misunderstanding, without visual cues conversations are blind to our emotions.

3- a
Trolls, people in deep pain taking it out on others due to lack of compassion around them
People that are genuinely mean. Those that where bullies at school or those that where bullied so much they became bullies online.

If the above is offensive to you I do not mean to offend. See you do not know me nor see my expression when you read my blog.
With compassion comes a wider understanding of our humanity and this is needed in the social media era, and the next era that will be born soon.