Several studies have shown that the most vocally homophobic are often closeted homosexuals or have strong homosexual feelings they are trying to hide.
http://www.ncbi.nlm.nih.gov/pubmed/8772014
And certainly public experience supports that (George Rekers, Larry Craig, Eddie Long, Ted Haggard, etc etc, all vocal public homophobes who were caught in homosexual relationships)
Your brother may stop saying such nasty things if you point out that fact.