How do you deal with ignorant comments?

Hi all, my first post so bear with me! :) 

I was diagnosed in April this year at 38. It didn’t really come as a shock to me or my family. I was pleased in a way because I know the reason I am the way I am, and now I try to embrace my true self because I feel I’ve masked enough during my life. 

I’ve struggled today though. I told a “trusted” colleague at work and was met with an attitude that has made me wish I hadn’t. They questioned whether I was actually medically diagnosed (I am but it shouldn’t matter?) they then said that the differences I have and struggle with are “things everyone deals with lumped under the name of autism”. I was gobsmacked by this comment. 

I feel completely foolish that I trusted this person when usually I’m extremely private. Although I am aware that it’s their problem and not mine. I just wished I’d kept quiet. I thought this person would be supportive - how wrong I was. 

No one else is aware of my autism at work and I’ve been reluctant to tell others because it doesn’t affect my work and I believe peoples attitudes will change around me. I’ve occasionally heard people use the terms “spectrum” and “autistic” as a means to insult others. This offends me and scares me into not saying anything. 

I realise I’m lucky that I have my immediate family’s support, not everyone has that and I appreciate it. I just wonder if anyone else has struggled with telling friends, colleagues etc? How did you deal with ignorant comments?