Why do people criticize my ability to take care of my child but they cant take care of their own?

my inlaws sat there and told my husband we are bad parents becuz we couldnt cal of one day when our babysiter flaked on us because he couldnt take time of cause the holidays and i had no sick time cuz i caled of when they made my baby sick overfeeding her! so we r bad parents but what pisses me off the most is that his sister and parents said that yet his sister cant take care of her kids! they r dirty clothed in public not showered properly sick constantly. i love my niece and nephew but dread them being aroiund the baby cause i dun want her to get sick. then last sun we go to the park and we were yeled at for not having the baby bundled enough yet sge was double layered and had winter coat on and hat and everything and we were yelled at but his sis kids were both coughing and neither didnt have a coat at all she said she gave them medicine already so they were fine! why the hel r we bein yelled and criticized when clearly i know how to take care my kid it might be my first and shes only 6 months old but get some common sense! sorry have to vent im so fed up with them!