I agree with the person that suggested kind questions about 'why?'. I do think that you can diffuse hatred much better with kindness than by retaliation with more hate. Sometimes you do have to recognize a jerk when you meet one and walking away is the only answer.

I do support reporting the conversation to the personal manager. It is harrassment and it does create a hostile environment. Your conveyance to work is none of their business. It should be documented in her record.

Instead of the offer of another donut, you might try to figure a way to offer to help them try cycling as an adult. Maybe you could help them recapture their childhood experiences and create at least an occasional cyclist. Yeah, I'm a big stupid optimist, but hey, its better than cursing, slandering and being angry with every anti-cycling jerk I run into.

YMMV