I'm not sure either. I find that (in my personal opinion), mixing work and politics, despite they're being linked, is to me a disturbing trait.
To be clear, I'm talking about office talk.
If a co-worker does it, it implies to me he or she are uncivilized, and cause themselves and other people embarrassment. When co-workers do it, I secretly think of it as farting in public, or vomiting your ideas on my shirt, or drooling your ideas. Political thought is important for me, and I have my opinions, but I do not want to force them on other people, not in direct conversation.
From experience, most people I know hold deep political convictions and couldn't be persuaded to see differently in a short office conversation, so it's short of pointless, a waste of words and a waste of my time and everyone else's, just so someone could farting his ideas in my general direction, and feel a bit better about himself / herself. Note that this is regardless of whether I agree with their ideas or not.
I do enjoy reading other people opinions, whether they are the same as mine or different, in forums such as NH. But the key thing here is that this is a thing I do of my own volition, in my own free time, not subjected to it.
To contradict myself a bit: while I find Notepad++ author making a political statement with his software releases just a bit odd, it's not as disturbing as someone doing it in a direct conversation, and he also does it a pretty non-intrusive way, which I'm fine with. In a way I almost like it, it's sort of refreshing.
But that's just me. I'm not a very social person, though, so I guess my outlook might seem very bizarre to other, more social people.