Why are some people so bigoted and contradicting when it comes to opinions?

some people are so bigoted. They don't respect the opinions of those who disagree with them. They contradict themselves, implying stuff like "It's okay to have an opinion as long as it's an opinion I can agree with.", "Everyone is entitled to their opinions unless you disagree with me.", "You can have an opinion but you can't have an opinion that insults me.", "My opinion is better than your opinion.", "Your opinion isn't welcome.", "You don't have the rights to have an opinion." Basically what I'm trying to say is that some people can't respect the opinions of those who like what they despise and some people can't respect the opinions of those who don't agree with them. Why do they do that?