@triggerhippy,
does the famous chant aimed at Mr Beckham count?
(it wasn't anti-homosexual per se but it did revolve around prurient interest into what he got up to in the privacy of his own home and on that level, it was no different)
With regard to the OP, maybe the campaign needs to address those in the crowds who, perhaps, mistakenly believe that -not- joining in with these chants signifies that they are either gay or, at least 'sympathisers'.
Of course, if you're not chanting and find yourself surrounded on all sides by dozens who are (and are strangers, not 'your mates') , then it's going to take guts to stay put and not participate. Having paid good money for your seat, it's not as if walking away is a viable option.
Or is it? If you get to the ticket office before the match ends, can you request a full refund, on the grounds of abusive crowd behaviour?