Kids wanting to play at the next level s/b aggressive because they can't learn to hit if they keep the bat on their shoulder. I don't think the pitcher's control s/b a decisive factor in the batter's approach and a good hitter at the amatuer level should not be concerned about getting behind in the count. Sure you don't want them to swing at a terrible pitch, but even worse you don't want them to watch the first pitch fastball pass uncontested into the catcher's mitt.
My son only took pitches in LL as a 10 year old....only because the coach told him to. If your kid's afraid to swing because he'll be yelled at, his career is probebely over.
I would suggest taking your son to watch some good college hitters, they are often swinging on the first pitch, talk about how those players got to that level. Its attitude and talent.
You can't walk off the island.