In Dick's defense...
In response to the general theme of comments above: Dick didn't give Damien the costume - ALFRED did. Alfred is seriously pro-Damien-Robin.
Also, this conversation was badly handled, with misunderstandings on both sides. But you just know Tim is going to eventually realize what Dick was really saying - that Tim is his equal now and doesn't need Dick's guidance like Damien does. And Dick is going to realize (and regret) that Tim took the decision personally rather than professionally the moment he realizes Tim has left the city.
And when this arc is over, they will hug and make up. I hope.