There is some truth in that. I don't know if it applies to everything (I don't think so), but it applies to DC. When I was younger, I loved the John Stewart Green Lantern, but if you interacted with Green Lantern fans, there would frequently be those who would tell you that John is only there because of affirmative action, the real Green Lantern was someone else, and so on and so forth. Well, that their type of thinking won out over my preferences and DC essentially was telling me that I was the one who was wrong. That more or less blew me out from being a DC Comics fan, and now I only really keep up with their goings on for my own educational purposes rather than a sense of love or loyalty for the company or the characters.
So, whether DC was right or wrong, I'm living proof of DC losing a young fan because the company tried to push something on me I hated while more or less crapping all over the character I actually liked. That said, I'm sure there are some young people who became fans because of the decisions DC has made, so again, right and wrong are points of view, but it was clear that DC wasn't going after someone like me, who was a fan from watching popular cartoon shows. Now, some will say that people like me don't exist and don't boost sales and that's the end of the discussions. Ultimately, I don't think that's true, otherwise I wouldn't encounter so many manga readers who began as anime watchers. I think if that is happening, there is a problem somewhere with DC or American comics that is causing it, not because it's an absolute truth in and of itself.