He has the nerve to think he is within his rights to be angry with me.....?

It was dumb and immature of him to stay out until 5AM without contacting you. It was just as bad for you to say FU. That is a terrible thing to say to someone., unless you always want that person to be a complete and total enemy, and even then it is rude and accomplishes nothing. He hsa every right to be angry, and so do you. You need to discuss it in a mature manner. If you are immature enough to"spit" at someone, you need counseling. But he also need to know he was wrong. Only YOU can allow yourself to calm down.