I remember having to deal with a similar situation back in High School because baseball and winter sports went head to head constantly.
Honestly, if you don't want to play, they ultimately can't force you...regardless of how bad they want one way or another.
Tell them how much money you'll be saving them, lol...hockey is expensive as all hell to begin with. Also, keep pushing the idea, show them you aren't on some new flavor of the month and this actually means a lot to you.
In the end parents want their kid to be happy, and once they see you aren't bullshitting your way out of hockey to be a "lazy stoner" (I'm sure they assume this, it's ok...all parents do) they might side with you.
In the end, don't EVER do something you don't want to do in order to make someone else happy. Fuck that.