See, I disagree.
High-heeled shoes are uncomfortable.
Gay marriages are [fine][disgusting]. (I don't want to get into that debate, obviously.)
In both of these sentences, I'm not talking about specific instances at all. I'm using the term generically, just like "Lions are fierce hunters."
A lion is a fierce hunter. Lions are fierce hunters.
A high-heeled shoe is sexy. High-heeled shoes are sexy.
A gay marriage is a celebration of love. Gay marriages are a celebration of love.
Singular or plural can still be used in a generic sense.