While I don't accept Schlesinger's Cyclical theory entirely, I do think he was at least partly correct.
His theory basically goes that a "self-generating and autonomous" cycle occurs from the people themselves rather than from leaders and that cycles of political action occur because the population becomes disenfranchised with the current system. This disenfranchisement brings in a new political mentality and explains political shifts.
If this is true, and I think it is in the broadest strokes, than it would make a great deal of sense to be nice to the political opposition to avoid extremes in cycles, or a pendulum effect.
Just days ago, a bomb was exploded in the general area of Ramkhamhaeng university. From what I hear, it was likely a "red shirt" versus "yellow shirt" issue. Whether or not that is true, I think it proves the point. Extreme partisanship only increases tension, polarizes groups thus preventing them from reaching consensus, and causes instability.
If we want a peaceful society, and this goes for all societies than we need to recognize that there is no group of people who are inherently more irrational than "us", whatever your "us" may be. Taking strong lines against those with different political and social views and life-styles may help your side to eventually win, but it is also going to create a strong group of people who are going to fight just as hard to replace your ideology with theirs.
This can be the relatively mild political instability in the United States or Canada, or the much more vicious instability in Syria or Nigeria. A hard line against groups you don't support may work in the short term, but in the long term it is much better to try to reach some sort of consensus and to negotiate with the understanding that you, and your views are not infallible. But, if you can't accept that you could possibly be wrong, than at least accept that you are going to win more friends and converts by being a bit more diplomatic.
For those of us living in relatively stable political situations, we need to realize how rare those periods have been in human history. We also have to understand that what seems normal debate now can easily become something that can rip people apart and result in violence.
I'm not saying that vigorous debate is not a good thing, but I am saying that whatever the debate is, you should still be able to get along with the opposing side. The highest degree might be a true ability to see past differences, but even a respect for the other probably suffices. At the very least, let others live their lives and don't assume that you are completely right and "the other" completely wrong.