If you think this skit is promoting homophobia you need to work on your media literacy. If anything it's lampooning homophobia. The entire situation is portrayed as being absurdly focused on the witness' (alleged) sexual orientation.

Just because you portray something doesn't mean you endorse it. Alan Howard portrays the ring in the Lord of the Rings, That does not make him (or the movie) evil incarnate. Similarly Stephen Fry portrays a barrister with a weird obsession with lesbianism, that does not make him (or the skit) homophobic.