Well, that's their tragedy isn't it? You can't turn down billions in possible tourist revenue because of archaic, outdated, discriminatory religious prejudices that exist in other cultures.
Besides, the majority of Muslim visitors would probably never see the gays,only during Pride. Many more would be tolerant or accept the laws and ideals of the country they're in, as they insist you do in their country. Not to mention that some gay Muslims (yes they do exist) would be grateful to go somewhere that welcomed them.