Are you really saying that it is ok to bash someones head because you believe in something and they dont?
I think the terms 'bash head in' and the verb 'believe' load the question somewhat.
We're not talking about beliefs but acting on those beliefs. For instance, there's a difference between someone having racist ideas and someone acting on those ideas. What we're talking about is action.
And yes, I think that in some circumstances it is acceptable to be violent as a response to the political action of others. More, I think everyone does. All we really argue about is which circumstances are justified.
I dont get why you think police have to believe in every rule they enforce?
I don't say that. But I don't see how anyone can respect someone who uses violence and coercion to ensure compliance with rules that they haven't thought about or actively disagree with.
I work in publishing - some books that we publish, I actively despise - should I forbid their publication?
I take your point that our employment commonly forces us to act against our consciences. But there's a degree of scale here. If your book were inciting some completely reprehensible action then yes, you should forbid its publication. If it's less of a big deal, then I understand why you would let it slide.
But I don't think the comparison really stands up well. The police are a lot more powerful than a publisher. Their actions have a huge impact, and much of what they do is repressive. Anyone who signs up to blindly enforcing all rules they are given - or will be given - and is prepared to use whatever violence and coercion it takes to ensure compliance abdicates their position as a person of conscience.
Unless, that is, they think that obedience to authority is more important than what that authority decrees. and it's that attitude that lies at the core of policing.