I see no issues with him jumping ship to Storm. The ball manufacturers are not very caring when it comes to dropping people from contracts when they want to do it, so while loyalty is always nice, it isn't usually shown in return.
What I do see issues with is bad mouthing Columbia after the move. As the OP said, it was Columbia products that made this possible for him. As Kidlost said, you can easily promote your brand without putting down others. And it would be nothing to say that the reason he left was that while Columbia makes good products, he has always done well with Storm, felt it was an opportunity he couldn't pass up, and allows him to help represent the company that he ball driller and friend supports, etc.