My FIL sometimes shoots out of his hip and doesn't realise the hurtful things he sometimes says. However, my husband doesn't seem to mind it. How should I deal with situation and ask my FIL to just "be quiet!"

if he doesn't live with you and visits occasionally, i would suggest ignore it and let it be...it's difficult to expect him to change at this age. however, if you all live together, i can understand how annoying it must be. have you tried speaking to him in a nice way without being angry? maybe he doesn't realise it yet as you said, but your talking to him about it will make him realise, and he will at least think the next time he does so.