So he confesses his feelings towards you, you tell him to give you time to think about, fast forward a undetermined time and you get into an argument where you probably told him a lot of things that were hurtful, after some time you come back and apologize for what you said to which he gave you a choice, to be with him or not....... and you called that insincere?
Are you like.... really stupid?
Seeing from his perspective, he worked up his courage to tell you his feelings (btw this is a incredibly hard thing to do because of INTJ's nature) you told him to wait, not only is this stressful, but whenever he meets you, he'll be tense about what he told you. Afterwards over something that's probably trivial you rage and spite him for the things he did, not only is this hurtful because YOU'RE ONE OF THE ONLY PEOPLE THAT UNDERSTANDS HIM, but because it's coming from the person he loves. Could you now understand his attitude that's just tired of being in a emotional roller coaster?
Sheesh can't people see from other people's views.