The speaker is talking to someone they once said "i hate you" to, back when the words were a cover for wanting that person to love them. Now the situation has flipped. If they met this person today, they say, they wouldn't repeat the phrase, and the reason isn't that old feelings have returned. The reason is that the words have finally become honest. What started as a lie, or at least an exaggeration, has turned into the truth over time.
The tone is bitter, blunt, and a little weary. The casual swearing ("or some shit") and the plain, almost conversational lines make it feel like an unfiltered confession. The speaker admits to being non-confrontational, which explains why the hate stayed unspoken. The repeated "i hate you" at the start and end works like a frame, but the meaning changes: the first time it's a defense, the last time it's a conclusion. The poem leaves us with the sadness of watching affection slowly turn into something harder.