Trying to convince other people of MY political leaning goes against one of the central political leaning that I have: Everyone should have freedom to believe in whatever they want to believe in. I also find it annoying when other people try to shove their believe down my throat.
I try to view political discussions as helping to spread information and confront one's own biases. Most people don't seem to though. I've had people that I agree with politically on a subject yell and curse at me because I don't believe every bullshit "fact" they sling my way.
In fact, many people do not want to try and have others convince them of their political leanings.