Gay conservatives: how have the Tories flung open their party closet*, while Republicans keep keep nailing theirs more tightly shut?

From UNC-Chapel Hill professor Andrew Reynolds' New Statesman article on the 2015 UK election:

The Conservatives put up more openly gay candidates than any other party: 39 men and three women. Of their 13 out MPs at dissolution, 12 stood for re-election and only one lost (Eric Ollerenshaw in Lancaster and Fleetwood) but his loss was made up for by the election of Ben Howlett in Bath. Howlett overcame a huge Liberal Democrat majority and was one of the sparkling Tory victories of the evening. A quick analysis of the 50 races where there were competitive LGBT candidates shows that Tory LGBT candidates performed considerably better than their straight colleagues. 72 per cent of them had larger vote share increases than the national trend, and on average their gains were three times the Tory average.  

This is fascinating from an American standpoint: US conservatives go on all the time about Margaret Thatcher and spurned busts of Winston Churchill and how the Tories can show us a thing or two about economics. But I haven't been able to find anything, in all the US conservative commentary on Cameron's triumph, about why Americans on the right continue to find gays a more useful punching bag than ally.

*The newly-appointed Equalities Minister, who was one of 128 Tory MPs to oppose marriage equality, has suddenly discovered she is all in for it.