I get it and I hope you do too. Always assume the person you are sleeping with is HIV positive and protect yourself.
Whether the other person is open, honest and upfront about their HIV status before sex; you would not have anything to worry about because you will always insist on protection, right? Well, what if you knew for a fact that other person was HIV positive?
If you are HIV negative, would you have protected sex with OR begin a relationship with an HIV positive man?