"wasn't Jesus's whole thing being that he loved all?" That is a good point, but you can't get Love confused with Disappointment.
God commanded us not to do certain things because they're sin. Just because God loves everyone, doesn't mean he's gonna be happy with us doing things he commanded us not too.
In 1st John 3:4 it says "We know that we have come to know him if we keep his commands. Whoever says, “I know him,” but does not do what he commands is a liar, and the truth is not in that person."
God loves us all, but you can't just go murdering people, stealing their things and breaking all the other commandments and sins and just expect God to be happy with you. Just like how your parents love you but they still beat ya tail if you do something wrong.