Handling parents

Idk where else to post this. I coach a group of 7 year olds and it is a more competitive level, so we’re moving away from beehiving to structured play. So my job is not only to keep things fun but teaching and introducing positions. Passing, control… First week of practice a parent calls me to tell me I’m centering the entire 10 player team around my child and that bc my child has #10 as well, it’s nepotism. Said he stands behind his opinion that my kid is a nepo baby- 7 yr old btw. I didn’t say anything. He’s ultimately upset bc his son was given defense position. However kids are all aware they will play more than one position but we have to start somewhere. Our program is similar to club but a bridge between rec. said I was holding his kids back. It really tore me, I work so hard to coach these 7 year olds and teach them the foundations. I’m hyper aware of favoritism and so my son isn’t our striker. He’s a winger. My son does have #10 but everyone gave their top 2 numbers and nobody else wanted 10. He didn’t know that- his son was joining a returning team. Anywho makes me want to quit ABs calling a kid nepo baby at this age is extremely rude..