He was upset and he took it out on Dylan.
He didn't explain why he was late and he didn't let Dylan explain what were those guys doing at his house. He just snapped at him, assuming he had a setback to his old habits. And he also implied that he had sex with someone else when he knew Dylan planned to confess to him.
I know he was JUST r*ped by his ex and he had every right to be angry, but it was an unfortunate event for both of them. Even though Theo had it harder, Dylan was also upset because he didn't know what was going on and was stood up.
To me, that apology looks more like "I know we were both wrong, but let's make up".
I'm confused.. what does Theo have to apologize for?! I don't like arrogant mofos like Dylan so this is irritating me.