Sometimes, due to:
1. Them restricting me (e.g. sleep early, no doing this, etc.) or nagging at me
2. Them scolding me or doing something I do not like (e.g. a friend blocking me on a website, poking or beating me up)
3. Them being horrible people (e.g. murderers, rapists, terrorists, Yahoo Answers or Youtube trolls)
Generally I do not hate people, unless if they fall into either one of those three categories. If they are of the third kind (such as ISIS, North Korean government or soldiers, terrorists, extremists, politicians who say hateful things), they are less likely to be trusted.