Englishman, maybe your observation is most applicable to American xdubbies, as their european counterparts seem to resort to America bashing as their new religion. Anyway, I think patriotism can easily lead to nationalism which can be very dangerous. Also hurting people's patriotic feelings can cause them float towards nationalism. One has always keep this in mind when discussing international politics.
Polarization led by emotions usually leads to less understanding of opposing opinions and less willingness to try and understand those other opinions. Anyway, I've seen emotions block the way to rational discussion in the politics section and it has resulted, more than once, in unneccesary name-calling on both sides. I usually try to stay out of discussions going that direction, but I do like to express my opinions on international and American politics