I can say that I've met all of Dream Theater - minus Petrucci - and they were all very friendly except for LaBrie, who acted quite arrogant. That includes Portnoy, who while certainly loves the spotlight was very down-to-earth. I don't agree with what Portnoy said because it is quite unprofessional (as Black Wizard stated), but if he truly is insinuating some dissonance between LaBrie and himself it would not come as a surprise to me. I've always thought that LaBrie acted like a diva, and while Portnoy has shown his fair share of insecurities and annoying habits over the years, he never stuck me as arrogant or ungrateful.
I've been hoping they'll replace LaBrie with a singer who has a similar high range but also has balls and depth (e.g. Russell Allen, Tommy Karevik, etc.) for some time now. LaBrie's breathy voice works well in many of their songs and his highs are excellent after being doctored in the studio, but I have never been a live fan of his. Combine that with his annoying arrogance and I'd love to see him replaced.