Hate... hate?

I was recently taken to task for saying that people like myself shouldn't hate extremists as hate itself is bad.
So, if we aren't allowed to hate those who would do us harm, what are we allowed?
Can we disagree with them? Because we have been doing that quite loudly and so far it's not worked.
There are Nazis openly marching in America and in the UK, the right wing of the Conservative party has the government in a death grip they seem unable, or maybe unwilling to break out of.

Meanwhile we have actual hate "preachers" such as Nigel Farage and Katie Hopkins trying to use anything that looks even slightly like terrorism to spread their vile lies.

So, when, if ever is it OK to hate these extremists? When they are marching on the streets with guns and torches? When they are using cars or bombs to maim and kill those they disagree with? When they run  entire countries and use lies to whip up their supporters into a frenzy? When they use mass surveillance to pinpoint those who would speak up or take a stand against them?

Or can we hate them when they use the state apparatus and social media against us and herd us into camps to concentrate us? It hasn't happened in the west yet, but it's not very long since it last did and history has a nasty way of repeating when we forget it's lessons or try to pretend that loving your enemy has any useful effect.

Thus far, all not hating and standing against extremism has done is to give carte blanche to them to go on and build power in the very countries that stood and fought against everything they represent.