I've noticed recently a lot of people giving elaborate arguments for why this or that justifies 'incivility'. I'm not really sure there's much to be made of the trend on its own; you can always tell when people are getting desperate and clutching at straws in politics by the fact that they stop to try to convince you at great length that they would be righteous for doing what by definition decent people try to avoid when possible. People who honestly think they have righteous cause don't beg for approval.
But in a sense my cynical view of the underlying motivations is neither here nor there. What I've noticed, though, is a common mistake in discussions, namely treating 'incivility' as if it were something symmetrical to 'civility'. But this is not possible. A general state of civility can be a coherent and unified thing, but 'incivility' is a term that covers a lot of very different things, and it is useless to talk about incivility unless you specify what, precisely is meant. Are we talking about insults (as if they didn't already exist in spades)? Death threats? Occasional harassment? Harassment campaigns? Vandalism and destruction of property? Burning people's houses or businesses down? Lynch mobs? Assassinations? The differences matter. And against whom in what contexts? It can hardly be the case that the argument is for a general state of incivility to everybody all the time. Is it to everybody one disagrees with? Some subset of them, marked out by some particular criterion? What restrictions are there as to time and place? The differences matter again.
Civility in the strict and proper sense is the behavior required to maintain the normal operations of civil society: people keeping the peace in small and big ways by acting in a way appropriate to living together. The ways one can fail to do this are legion; if you don't specify which you mean in particular, and the conditions and restrictions on it, it is impossible to say much on the question.