That’s a big point, isn’t it? Because Kurt has always known that he’s worthy of being loved; Kurt’s had Burt to reinforce that every day of his life, and now he has Rachel, Blaine, Finn, and Carole to further prove it true.
But Blaine has had Sadie Hawkins, Cooper, his father, and now the Warblers to teach him that love is conditional. When you’re not needed, when people lose interest in you, when you stop being what they want you to be, people stop loving you. Love is something you earn and something you have to fight to keep.