I think it's easy to read as just plain homoeroticism - the book's laden with it, esp. in subtext, though sometimes explicitly. You'd have to consciously work to not see talking about the delight of men pressing into other men while fondling sperm otherwise. When he's talking about gaining pleasure from a man's thighs while in bed with him (a bed that previously was described as a marriage bed) it's also really hard to read in any other sense. "Queequeg's arm thrown over me in the most loving and affectionate manner... You had almost thought I had been his wife," and "hugging a fellow male in that matrimonial sort of style." Or, "there is no place like a bed for confidential disclosures between friends. Man and wife, they say, there open the very bottom of their souls to each other . ... thus, then, in our hearts' honeymoon, lay I and Queequeg - a cosy, loving pair."

While Moby Dick was slightly more subtle, Billy Budd and Melville's letters to Hawthorne and are even more heavily loaded with homoeroticism than Moby Dick. Homosexuality isn't a new thing.