Why is the comments section on Yahoo articles a cesspool for right-wing fanatics?

It's been that way for years and I've been fairly curious about it. Most comments on any politically-oriented topic on Yahoo articles are from right-wing fanatics, and comments supporting their talking points often get 10 to 1 or 50 to 1 thumbs up vs thumbs down, incredibly skewed compared to the balance of public opinion (elections, health care, gun control, Ferguson). What are the reasons? Other comments sections (such as CNN) have heavy right-wing skew but typically not as bad.

Some possibilities:

1. Reason: Paid shills with multiple accounts quickly posting talking points and thumbing them up, in an effort to influence public opinion by having the "popular" comments be inane right-wing talking points. If so, why are there few paid shills on the left to do a similar thing? Anyone have inside info on this?

2. Reason: Those with Yahoo accounts heavily skew to the far right. If so, why?

3. Reason: Those with extremist right-wing views tend to be more vocal to begin with, and most want their opinions heard and approved of, more than those on the left. Then why is Yahoo so much worse?

4. Reason: Yahoo news feeds end up funneling political articles to right-wingers based on their previous clicks, so they are mostly read by them. This would support the notion that the far right is more interested in politics.

5. Reason: Right-wingers have much more time on their hands.

6. Reason: Positive feedback loop. Some combination of 1-5 gives right-wingers an edge in presence, and all the thumbs ups just encourages them more, while the quick thumbs down and insults discourages moderates/progressives, resulting in the much larger ratios noted above.

What weight would you give to these reasons and what others would you include?

Any studies done on this?