Vote blue no matter who is a political slogan, not an order with any weight. It's not like people are prevented from voting Republican in any way.
Stein was arrested because she didn't meet the polling threshold to be eligible to be considered as a candidate and then tried to force her way on stage. It's no different than you or I going to hear a band play and trying to force our way on stage because we thought we could play guitar better.
Facts are facts. She was not a political opponent because she did not get enough support to even participate in the debate. She was arrested for breaking the law, not for being a political opponent
It's a representative democracy. If we can't agree on at least this, then your opinions are not grounded in reality and there is no point talking further.