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.
If nobody ever settled the Vi vs Emacs debate there's absolutely 0 chances we're going to settle more complexes debates with real life implications so it's better for everyone's enjoyment of our global community if we could agree to keep politics were they belong and not everywhere.
Sure, I get (as sibling commenters point out) that this can be tiresome, but just because something bores you doesn't mean pretending it doesn't exist is productive or progressive.
I think your opinion here is a commonly held one, which I find increasingly frustrating and bizarre.
I personally feel that work and politics are by definition inextricably linked, and attempting to separate them as some sanctimonious attempt at taking moral highground is naïve (at best, insincere at worst). Which makes the use of the epithet "immature" here particularly ironic.