I can only answer for myself. I hate sex offenders, those who kill others unnecessarily and a few other criminal types...but I am not prone to lengthen my list.
Likely. Hitler didn't just hate one group of people. That's why Martin Niemoller gave included different groups in his “First They Came…” speeches at different times. Hate is a strong emotion that needs to be kept in check. It's okay to hate what is bad like an action, but when directed at a person, it can be real bad.
Look at Cains hatred and anger towards his brother. (Genesis 4:5-8) he did not look with any favor on Cain and on his offering. So Cain grew hot with anger and was dejected. 6 Then Jehovah said to Cain: “Why are you so angry and dejected? 7 If you turn to doing good, will you not be restored to favor? But if you do not turn to doing good, sin is crouching at the door, and its craving is to dominate you; but will you get the mastery over it?” 8 After that Cain said to his brother Abel: “Let us go over into the field.” So while they were in the field, Cain assaulted his brother Abel and killed him.
I'm not sure. It might depend on personal experience and character. For instance, if Jill has had several negative experiences with individuals who bear similar characteristics, she might then assume that all people who have that trait will treat her in the same way, and then avoid them. And by avoiding, she might never have the chance to discover that assumption was a mistake: a category error. Or, if Jack grew up in an area where everyone was the same, he might feel an anxiety whenever he meets others with different appearance, speech or behaviour. His anxiety might cause him to say or do things that trigger conflict from the start. But in areas where people see specific others as the enemy, they might target only one group and see others as acceptable. For instance, in Israel (gross generalisation only) there is more tolerance for Christians than for Muslims; while in Ireland the Anglicans and Catholics despise each other but can be quite comfortable with immigrants of differing faiths. I found this site which you might like: https://www.psychologytoday.com/blog/out-the-ooze/201607
