I've adopted a policy where if I get this crap from someone - conversation over. Too bad for you if you needed me to watch your dog, expected an invitation to stay with us in Wine Country, wanted a reference for a job, etc... I approach those who show an anti-cyclist bias the same as I would approach someone making openly rascist comments. Ostracism. It's a bit more difficult at the office but with the numbers here that ride into work, it's pretty obvious such commentary will not help your career.