Based on my experience, I would say that you don’t want to put the focus on trying to prove the intrusive thoughts false. As doing that and/or trying to just push the thoughts out of your head, usually will end up increasing them. Instead try to let yourself sit with the thoughts without engaging with them. Also, try a neutral response like “maybe it’s true, maybe it’s not” or even “thanks”. Also, It helps me to remind myself that just thinking something doesn’t make it true. A therapist once gave me an analogy about thoughts not being facts that I still think of, when I need grounding regarding my OCD. She said “just because I say I’m a tomato, doesn’t make me a tomato”. When I heard that I thought it was silly and random. Then I realized that’s exactly the point.