That's why you have to practice the correct social timing to cut in with "Do you think she's ugly?". If you're ashamed of your opinions--"Oh God, I think redheads are ugly, and thus have insulted his wife!"--they'll pick up on that and a fight may ensue. If you skip the illogical guilt and move on to the truth: "My opinion has no bearing on his wife being 'objectively' beautiful or not," you are much more prepared to avoid a violent confrontation, both in your diction and your demeanor.

Though it's probably easier to say "red-heads aren't really my type," which expresses the same sentiment but with less of a loaded word. Thus, you provoke a milder emotional response, have communicated your feelings honestly, and can go back to picking out cute girls sooner.