Why do some people speak without filters?

I have an almost 3 year old. He runs, jumps, screams, cries, throws, hits, bites and gives the BEST hugs. He also attends preschool 5 (yes, FIVE) days a week. His mommy doesn't have the choice of staying at home. He is there all day. The school I chose for him is nestled in the middle of 3 communities and is a faith based school. They teach him his numbers and letters, songs and verses. They reinforce my own beliefs that God is our Creator and Heavenly Father. They demonstrate true and unconditional love to him, even though some may dub them only a "daycare." His teachers know him by name and are happy to see him each day. His friends scream in excitement when he enters the room.
Some families don't have to use a preschool. Some families have the ability to have mom (or dad) stay at home with their kids. This is awesome! This is amazing! Some families (mine included) don't have this option and are thankful for preschools and schools like the one my son attends.
So why is it then that some people who have the ability and luxury of staying at home with their kids look down and judge those of us who can't? Ignorance? Selfishness? Lack of understanding? All of the above?
I recently read a comment made by a stay at home mom. She said she didn't want to put her child in daycare because she was afraid he might "pick something up like AIDS." WHAT? This not only made me so mad I turned red, it made me sad. People really think like this? I felt like I needed to say something. OK, that's a small lie, I felt like I needed to say A LOT...to HER. I found myself trying to defend my choice of putting my son into childcare and that made me even more upset. Then I realized it, some people speak without thinking, without filters. Some people have opinions that are not fully formed.
It may not matter to anyone but me, but I HEART CHILDCARE! There, said it! Loud and proud! I do. I love the school I chose for my son. The teachers there are amazing and I wouldn't trade them and their love for my child for anything!
So, to the mom who made such a bold and uneducated comment, enjoy your time with your kids at home, they are special and unforgettable times. But please remember, while I am working hard to build a solid and comfortable life for my child, he is safe, happy, loved and most importantly disease FREE!