Yes, but he is speaking generally, to students who will (most of them) never be as deadly as he is. He has an excellent means, fully under his own control, of dealing with adult wizards: He is able to take apart a fully-trained Auror without breaking a sweat. He has no equally good means of dealing with a Dementor.
In “Humanism” it is stated that, if you don’t realise you are under attack, you can lose the ability to Apparate. (It’s a happy thought, presumably.) Quirrell is particularly vulnerable to the Dementor’s attack, same as Harry, so this might be particularly dangerous to him.
Quirrell says that dementors are the second most dangerous things, after adult wizards.
Yes, but he is speaking generally, to students who will (most of them) never be as deadly as he is. He has an excellent means, fully under his own control, of dealing with adult wizards: He is able to take apart a fully-trained Auror without breaking a sweat. He has no equally good means of dealing with a Dementor.
Just Apparate away!
In “Humanism” it is stated that, if you don’t realise you are under attack, you can lose the ability to Apparate. (It’s a happy thought, presumably.) Quirrell is particularly vulnerable to the Dementor’s attack, same as Harry, so this might be particularly dangerous to him.