Derek Hale makes poor decisions re: bridges, fire.
Sometimes it's really tempting to go back and make a log of every time Derek Hale burns a bridge by accident. And I say "burn" but I mean more "dramatically blow up and then salt the ground under". I'd actually forgotten that in season 1 he kidnapped Dr. Deaton and, you know, kind of tortured him a bit to try to make him turn into a werewolf. For completely internally consistent reasons that should have saved lives except that Derek was wrong and instead alienated someone who could have helped him and put everyone in worse danger. SOME MORE. (Note that Scott was not exactly a bulwark of good choices here either but for serious Derek punched Scott's boss a lot.)
(And Derek walks into the examination room in 1x06 without the mountain ash stopping him! After that, when Peter comes back, the mountain ash stops him! Dr. Deaton installed it specifically to protect his place of work against Derek, who he apparently thought might be a serious danger to him and Scott, based on, you know, Derek kidnapping and torturing him. I can't believe I forgot that this happened until I rewatched the episode this weekend.)
Given what Derek put Dr. Deaton through, I think what Dr. Deaton said to him was actually pretty gentle. Derek Hale is such a walking avalanche of bad decisions, man.
Insert usual note here about how I find his flailing incapacity not to alienate everyone in the world to be a basically sympathetic problem so long as he gets held accountable for his actions so that he can do better in the future.
... I am writing like ten thousand words in a document I've titled Derek Hale Had a Happy Werewolf Childhood, too, so this is not just pro forma not-hating-him. I have named his mother Marjorie, which I think is a nice name for a werewolf.