Second opinion: Does it have to be a sin to be something we should avoid? Technically smashing my finger with a hammer isn't a SIN, but it's probably not a good idea, even if I lost a bet or somebody dared me to do it. Blasting people in the comments section of a news article, political or otherwise, is about as damaging and pointless as the hammer applied to the finger.
Actually, if we take into account all the high blood pressure that is caused and the resultant toll on health, the political news article's comment section is probably worse for people.