I am a tenured math professor in the US. The top-rated answer suggests to be more assertive and forceful; personally, I think a bland approach might be effectiv

I am a tenured math professor in the US. The top-rated answer suggests to be more assertive and forceful; personally, I think a bland approach might be effective: Colleague: "I have an exciting new idea to design a new underwater basket-weaver!" You: "Thanks. Sounds interesting, I'm afraid I'm rather tied up at the moment." Colleague: "But if we build this, then agency XXX will give us $YYY in grant funding!" You: "Sounds great. I have too many commitments right now, but good luck!" Colleague: "I don't think you're seeing the opportunity here. Just imagine blah blah blah." You: "Sounds exciting. I'm sure it will be a big success. Best wishes on your project!" Colleague: "But... but..." You: "Thanks again for the invitation. If you'd please excuse me, I have to go back to work." [Put head down and return to your own work] You say you love working with people -- are there enough people whom you do like, that you can focus on working with them?