How should I handle my relatives who disapprove of breastfeeding?

Unfortunately there's nothing you can do about them running their mouths. Motherhood is as such. You breastfeed, it's wrong. You don't breastfeed, you're selfish. You work and leave your kids in childcare, you're heartless and missing out on milestones. You stay home to care for them full time, you're too dependent on your spouse and selfish. You can never please everyone in this life but you can decide what's best for your child. Turn a deaf ear on your relatives, and go ahead and breastfeed. They are not the ones who carried your child for 10months before popping them out, or waking up at godforsaken hours to a wailing baby. I'd say go into an empty room, get yourself comfortable and breastfeed your child at peace. Or if there is no spare room, wear your nursing cover and have your spouse (or someone nice) to engage in a conversation.