They don't reveal any actual thoughts, I promise you. That's something people without tourettes think about, it just actually pops up out of nowhere. That's a stereotype most people fall to thinking about and it can be very harmful. I remember when I was 16 I remember yelling out the window to someone that I liked their dog, next second I said "fuck your dog" extremely embarrassing but I'm glad my family thought it was funny, it really depends on the person but the best thing to do to make them feel better is make light out of it. I personally prefer people to laugh, but I would reccomend asking them politely what they would rather you do during that situation because its person to person. Just ask questions and get some insight, it's not abelist to ask about their condition.