The reason it's different is the same reason that every flame war on the internet starts - over text, you don't have any social cues, facial expressions, tone o

The reason it's different is the same reason that every flame war on the internet starts - over text, you don't have any social cues, facial expressions, tone of voice, etc to fill in the context. So your brain will fill in the gaps, usually using the worst interpretation possible. It's the road rage effect.