Welcome to the internet.
It's actually very heterogeneous. On the one extreme, you have ScienceBlogs, let alone certain specialist blogs that neither jerks nor idiots are interested in. On the other, you have... <gulp> ...YouTube comments. I don't think anyone with an IQ above 80 has ever commented on a YouTube video.
Even within Wikipedia you can find such differences.And to a slightly smaller extent, this holds for ScienceBlogs: Tetrapod Zoology is almost idiot-free, but all blogs that _ever_ talk about climatology or school shootings or other topics that are (at least in the USA) politically sensitive are regularly visited by ideology-driven people.
A core aspect of science is to move towards objectivity via mutually respectful debate
Surprisingly little respect is actually necessary for science. What _is_ necessary is that no participant resorts to logical fallacies like the arguments from authority, ad hominem, from ignorance, from personal incredulity, and the like. (Note that "insult" and "ad hominem argument" are not synonyms.)
After all, the reason why the ad hominem argument is a logical fallacy is not that it's disrespectful. It's that even a stopped clock is right twice a day.