Again, it was just my original take, but intense feelings can easily become hate when spurned.
It could work either way, but I'm basing it simply on Byrne's initial conflict between the two.Mantlo's later confession by Northstar to Wanda of "preferring the man you were" as an eye candy factor, not lust.
Would J-P have known that from their initial meeting? I'm not saying 'love at first sight' as I hadn't mentioned love, just feelings, but a physical attraction on first impression. THEN he discovered he was a bully THEN he started a relationship with his sister THEN he genetically altered his sister and distanced the two of them after only recently finding each other (in the grand scheme of things).Think about it. In their high school years, JP was a self-aware gay kid and Walt was a jock and a bully. It's very reasonable that JP would truly hate him.
That'd be enough to have feelings become confused as hatred, or even turn into hatred, and certainly enough to cause tension within the ranks.
But again, it's been years since my first reading and it was just my initial thoughts.