Is it justifiable to cut off a frined for having different opinions?

The question "Is it justifiable...?" in and of itself is purely based on opinion.

There's no such thing as unconditional -friendship, -love, -whatever. Some people are more tolerant than others, but every person has his/her limit.

I like white wine better than red wine, prefer Android phones over Apple's iPhone... that sort of thing is just expressing personal opinion and there's nothing wrong with that if yours is the other way round.

I wouldn't even have a problem with opinions such as "You look like a monkey in that suit!" or "You look like a slob wearing those rags"!

However, once a person starts attacking my civil rights, that person well and truly crosses my line.

E.g. if they say things such as, "Cycling should be banned, because there are too many accidents" or "There should be a mandatory registration/permit for keeping gold fish. Why should I have to pay for dog registration and other pet owners do not"?

Those are not simply opinions -- they're callous attacks on basic civil liberties and the people who believe in them.

They might as well tell me straight to my face, "I don't like cycling and I'll punch everyone in the face who still ride a bike". At least that is a far less cowardly way to say it and gives me the right to defend myself.

People who keep up such attitude won't be my friend for long.

It depends on what the different opinions are. For instance, if the difference is "what is the best cut of meat", that would be silly. If the difference is something like "women are inferior to men", that's a good reason, because you'd likely not have much in common.

That's a tough one.

If it's politics, then no. If they're making racist remarks, then maybe. Talk to them first about it. If they're making remarks about you, other friends, or your family, yes.

There is no "black and white" answer to this. But try to keep in mind that opinions and ideals change over time. If your friend's opinion is something that you can see not changing over time, or that YOUR opinion is something that you do not see changing over time, it might be a good idea to phase that person out. No need to do the "I'm breaking up with you!!!" thing.

ok if its a really good frnd probably best you guys steer clear of that topic...

Else if its just some guy you know and say "Hey" you can cut him off

If you let that stop your friendship, then they were not really that good of a friend in your eyes. If they are close enough to want to keep, then agree to disagree, and never bring the topic up again.