There's several reasons why this is the case. For one thing, it's draining. You argue and explain and grind away, and it never seems like you're making any progress. In the end, you're faced with a dilemma: explain the 101 material for the umpteenth time, or veer into more advanced territory that's off-putting to newcomers. A Grunted and Hinged post on beginners and burning out described this process in detail. My experiences with libertarianism/Objectivism conform pretty well to the model.
Politics is also mind-killery. I don't think I need to walk anybody through this one. We've all felt it, that frenzy when your beliefs are being attacked. We instantly lose all ability to reason, fixating on discrediting our opponent's position, no matter how eloquently the argue or how much evidence they put forward.
That sensation is a product of our ape brains, still mostly optimized for life on the savanna. To my knowledge, there isn't a direct solution for this, but there are a few hacks to avoid being in that situation to begin with. The most popular tactic is keeping your identity small--or, if you prefer more colloquial terms, "being independent." Of course, Independent and Person-With-A-Small-Identity are still identities, and people will attack you for them.
(If you're thinking "I could be independent without making that part of my identity," I'm afraid it's too late. You also just lost the game.)
Furthermore, there's usually a reason someone starts identifying with a particular ideology or movement. You don't wake up one day saying "I think I'll be a feminist!" Going back to Gruntled and Hinged:
Let’s oversimplify a bit, and presume that the only question that feminism seeks to answer is whether or not women and men are equal. So you, New Feminist, get involved in feminism (for the purposes of this exercise, and because I’ve already slightly oversimplified, please assume you’re female). You start identifying as a feminist, and as a result start having conversations/arguments/discussions about whether or not men and women are equal.I emphasize this point, not to comment on feminism, but because your beliefs necessarily contribute to your identity, which then contributes to your behaviors.
Take my own example. I decided I valued natural rights, the Constitution, and limited government, and consequently began thinking of myself as a libertarian. Since I was a libertarian, I began discussing libertarian ideas. Wasted countless hours on the internet arguing about politics, and wasted my vote* on Gary Johnson.
But what did all that accomplish? I stressed over things I couldn't control and didn't shift the political landscape significantly. Meanwhile, my education (both formal and informal) languished. I paid the price for that, too--itself a reason to get out.
So now, I'm realigning my identity away from politics. My beliefs have shifted** and so have my priorities. How I label myself is important, because it's a way of caching the self. What political label you use will impact the direction your beliefs update. As a libertarian, I became more anarchistic and extreme, as a radical centrist the reverse occurred.
You should also try to replace the symbol with the substance. For a long time, I called myself a nerd, because it seemed like an accurate identifier. Even if we ignore the social connotations, though, it wasn't very useful. Nerd implies a lot of things to different people. For me, however, it referred to a relatively succinct set of interests in ideaspace. Now, I'll say "I'm interested in philosophy and spaceflight" instead of introducing myself as nerd. I still am one, but a very particular type of nerd.
The same goes in politics, but that's a lumper's game. Nuance dies upon first contact with the political. If you want to talk about complex ideas intelligently, getting out of politics is the way to go.
*I don't actually consider my vote wasted, since Romney was guaranteed to win Kansas. You could argue that voting at all was a waste of time (especially since I had to do the mail-in forms), but I was 18 and really wanted to.
**More on that later.
