Step parents + discipline

I have just recently started back dating (I’ve known this man since my son was 1 he’s 3 now) we split for some time & I’ve since had another baby we now live together & he feels I allow my 3 year old to do “anything” my son is your typical toddler he cries, he wants to cuddled but most of all he’s obsessed with his mama, I allow any adult other than me in his village to correct him but when things begin to turn physical I don’t allow it. I’m not one to physically discipline kids let alone a 3 year old. So we’ve now had a huge disagreement & I told him I will never allow him to discipline my children. He doesn’t have kids btw (not that it matters but it gives perspective).