The thing is that there are pro-leave parties in many other countries, and the parties in power (all pro-stay) are fighting them to stay in power. The same kin

The thing is that there are pro-leave parties in many other countries, and the parties in power (all pro-stay) are fighting them to stay in power. The same kinds of argument are made everywhere, with the pro-stay parties predicting bad deals for the leaving country, economic trouble, et cetera. They probably honestly believe that will be the result for a country leaving the EU. Now the UK is leaving, and the deal they get must be approved by all remaining countries (they all have vetos). Of course those countries will only agree with a harsh deal for the UK -- one, they really already honestly believe that that would be the result for any leaving country, and two, it is great ammo in their fight for power against pro-leave parties in their own countries. They get to show that their predicted doom comes true. I'm not sure politics is always hating "the people who have a different opinion", but it's certainly doing everything to get power in your own hands instead of theirs.