My question is, to put it bluntly: why would you tarnish or ruin a (assumed) good friendship based solely on this decision? 

I'm asking because when your children go to the store, to the play ground, to a fair, to a restaurant, to the doctor even, you don't know how many of those children aren't vaccinated or may even have more serious diseases. How do you know they weren't born to a parent with HIV, Hep C, etc.  and contracted  it or contracted it early in life? (I know they are blood born but if they're playing you never know how cuts or bumps or running into each other may happen) 

These are honestly just thoughts I've had because my friend is like family we just have different parenting styles as you'd expect mothers to have but that doesn't change my love and respect for her. We always keep the kids separated even when sick just like we do with our other friends children. 

Edit: I understand your perspectives and I'm not bashing you. Just curious how you'll handle having your children in public? Same as normal? Since the medical care of strangers is unknown. I guess I'm just intrigued by how others view things want to fully understand their approach. :)