I was in Morrisons yesterday - looked at the magazine section. There was the "men and motors section" - all the "male porn" magazines plus car stuff, Newscientist, Economist, National Geographic and some other stuff.
I mean... it sounds more like he's internalised a few things his friends have said rather than looking at a few commercials of children interacting with various toys and creating a message just from that.
I think you are projecting your guilt a little and avoiding commercial TV won't stop him getting or buying into these kinds of messages. Though it may help.
My kids didn't watch any TV until they were over two, and no commercial TV until much later. Still, they started talking about "boys" things and "girls" things as soon as they started mixing regularly with other children. Firstly at a creche at my gym and later at nursery school. I know the creche didn't deliberately encourage gendered thinking like, they went out of their way to promote inclusive play. But my kids picked things up anyway, I presume mainly from the other kids.
I don't think the answer is to sequester them away. You need to keep talking him about it, and get his dad to do it too.
Although I guess it may not be coming from the TV, that might just be me projecting my guilt at how much TV he's watching atm?!
He could also be picking these messages up from nursery I guess. He knows an awful lot about Ben 10, for example despite never having seen an episode. He gets that info from playing Ben 10 games with his friends.
An exchange with DS (aged 4) this morning: (DS had been watching TV and an advert for a pink girls' toy came on.)
DS: I like girls but I don't like girl toys.
Me: Which are girl toys?
DS: Pink toys. I like it when there are blue ones.
Me: Girls like pink?
Me: Who told you that girls like pink? Was it the TV?
DS: I remembered, my body told me it.
Me: Oh, I see. Can I tell you a secret? Sometimes the TV says that only girls like pink and only boys like blue. But let me tell you a secret, that's not true! Some boys like pink and some girls like blue. I like pink, and Daddy likes pink too.
DS: I don't like anything pink! I just like blue and red. <getting quite cross now> You're talking rubbish mummy. You're not my friend anymore.
I'm not happy to admit he's being watching enough ads to affect his thinking in this way (if that's where it comes from). I really don't like him watching ads, and pre-motherhood didn't think I'd allow it.
But the reality is we're insanely busy atm (moving house) and I must admit there's been quite a bit of the old electronic nanny going on, and he's at the age now where he's growing out of some of the stuff on CBeebies, too young to be interested in everything on CBBC, so we've been straying into the evil world of commercial channels!