This is especially common, and especially important with, SF. Look at all the classic SF authors:
Heinlein: right wing bordering on Fascism. Stephen Baxter very cleverly follows the ideology in the Destiny's Child series, and paints a biologically successful H. Superior, but isn't shy about the downside. While I doubt Baxter share's Heinlein's political philosophy, they both ask the question "are there elements of aggressive, expansionist policies which by definition must be adapted for the long term (post-Sun) survival of our species?"
SF has a long tradition of exploring human themes, however good or bad they may seem now. Personally I have no problem with homosexuality, I see it as a completely normal sub-group of humanity (meaning a minority rather than "worse" in any way), but if an established SF writer who's books I previously enjoyed writes something then I'm going to judge them on their writing, not their personal views.
If he oversteps the mark with his arguments against homosexuality then I'll get involved and argue back directly against him. But it's a different matter to SF.