That's sad and extremely ignorant!
My Exmed Cancer group was a combination of different cancers and different stages.
We had an afternoon tea together where we could talk about our treatment if we wanted. I was fascinated to learn one lady, a little younger than me, had been diagnosed triple neg in one breast and HR positive in the other breast. A couple were stage 4 but very relaxed and giving. One was BC and the other Hodgkin's Lymphoma.
Don't let their ignorance spoil it for you!
Take care and best wishes with ongoing treatment