“Don't be so closed-minded!”

Your new boyfriend has a tattoo. Your father doesn't like your boyfriend because of it. When your father complains about his tattoo, you say:

Don't be so closed-minded!

Don't be so (adjective)

Use this when you don't like the way that someone is acting:

Don't be so lazy.

Don't be so shy.

Don't be so wasteful.

(someone) is closed-minded

A "closed-minded" person dislikes things that are new and different. In the example above, tattoos are traditionally thought of as being for bad types of people. If your father believes that, and won't change his mind, then you might say that he is "closed-minded."