is there something about the medium itself that discourages it?

Yes. The way the internet is designed , especially social media, news and advertisements creates lower attention spans and thus people don't have the stamina or patience to read hard things.

Another reason, and this is not due to internets, is that educamation has been democratised. Some people if they are presented with information they don't know or that requires some thought say they are being discriminated against.

Another is that it's hard to analyse and refute logical fallacies . It takes a lot of expertise and practise to see how discussions are hijacked or influenced.

People will say nothing rather than risk being called racist or sexist and thus nuance is lost.

It bothers me when thinking and questioning is said to be supporting racism, sexism, etc etc. This is the opposite of freedom and only evil thrives in ignorance.

The refutation to most difficult issues and situations is. "I really want to help people and this is such an important issue that I am going to think about this and find out more. "

Please, in all issues listen and discuss. Changing people's minds or tolerance of difference is not easy but it's better than hate and division