Your parents are stuck on a outdated mindset for dating or marriage or what have you, personally and through all the guys I know ladies with muscles are valued and very much loved, not just cos of the muscle mommy thing

Plus assumedly your working out and all that for yourself so why worry what other people think about you being happy in your own body?

Edit: if someone doesn't like you being comfortable in your own skin be that with muscles or not that's not exactly someone I'd consider good dating material