Very interesting post. The only thing I disagree with is:
when terms like "evil" or "nazi" or "moral fibers" or "slaves" or "rape" are used to describe fairly normal differences in opinion, the only possibility is a (usually non-productive) escalation of anger and hard feelings.
Responding in kind or escalating the situation is not the only possibility. It is possible to either 1) not respond or 2) respond without emotion. Take your second example:
PC guys are Wintel slaves perpetuating a monopoly of Evil corporations raping consumers
Rather than take that as a personal attack, respond to the actual argument -- that using a PC means a person supports Windows and Intel. Simple, unemotional rebuttal: I use a PC and run Linux on my AMD chipset (no support of Windows or Intel). No emotional response, just a simple rebuttal.
Why do many feel it necessary to use such hyperbole? I have two ideas about that.
First, Freedom of Speech does not necessarily mean you will be heard or paid attention to. It is not the freedom to speak that many want, it is the attention to what they have said (whether positive or negative). I find it interesting that you included the word apathy at the end. So many of our society's extremes are an attempt to overcome a general apathy and get attention. Movies, advertising, roller coasters, extreme sports, newspaper headlines, and forum trolls are just symptoms. Why is society so apathetic to begin with?
Second, these wouldn't be topics of interest if there wasn't disagreement. If the facts were 100% clear and indisputable, it would not be an issue. Because each side believes it has "facts" that prove it's argument and the "facts" to disprove the other's "fallacies", it is an issue. We all want to be right about thing - to believe we know what we are talking about. So, an issue that we believe in becomes an emotional investment. That leads to emotional arguments and hyperbolic posts.