Why are people surprised when I'm political

I just wanted to rant about things that happen in my personal life when it comes to people being surprised im political. I attend a university where there are a large handful of conservative people. Throughout highschool, I dressed quite "apolitically," usually a band shirt, skinny jeans, a beanie and hoodie, I feel like thats a quick give away that I'm at least a liberal but I guess its a surprise to some when they find out how political I am. In highschool I remember my friends being surprised by how political I was and told me to be less political (we were having a political conversation, I usually dont bring up politics unprompted). Even people on discord in music communities are surprised when I have strong political stances. 

I am pretty open about my interest in hardcore and metal music. So I guess people don't know the history of those genres, which I dont expect them to. But in discord servers that cater to metal and hardcore fans, why are they surprised that someone who listens to music associated with political activism, human rights, hating cops, anti war, anti racism. all that, why are people I meet surprised when someone who listens to music associated with political protest is political. People are shocked when I share similar views to the music I listen to. It just blows my mind how people meet me, get to know my interest in these things, then later get surprised when I am vocally political on my instagram or on discord, especially since the servers I am in have common interests for bands like Black Sabbath, Rage Against the Machine, and System of a Down. 

just wanted to vent my confusion.