Like millions of conservatives, I get a lot of my news by reading Drudge Report. In such stories, almost all the commenters are likely coming from Drudge, so they are probably slanted conservative. I often will look for the same story on a different website just to compare. Similarly, when I come across a comment thread that has a lot of white activist comments, including the obligatory “antiracist is code word for anti-white” meme, I Google the title of the article and the word “Stormfront.” Usually, that infamous forum linked to the story.
I do get the impression that comment threads seem to measure intensity. I remember in 2010 the vast majority of comments in all non-liberal publications were very anti-Obama. Though his approval ratings were low at the time, I felt that the anti-Obama sentiment was even stronger after reading those comments. In the run up the 2012 election, it seemed like there was much more anti-Romney comments than anti-Obama comments. This was just my impression: I did not do any analysis
Re Derbyshire’s impression about gun control being less unpopular than immigration: A friend works for a Congressman who is very outspoken against the former and solid, but relatively silent, on the latter. The friend tells me that the Congressman gets hounded by phone calls from outside his district critical of his opposition to gun control—but that virtually all the calls from his district are against amnesty.