I'd be more convinced if somebody argued that Ennis and Jack were both looking for the love they never received from their fathers. We know Jack's father was openly contemptuous of Jack, and Ennis' father made Ennis look at the dead Earl and then got himself and Ennis' mother killed in an automobile accident.
Isn't that at least part of a "classic" Freudian explanation for male homosexuality, an emotionally distant or absent father?
(I mean "convinced" as a Freudian explanation, not necessarily convinced as in "correct.")