Rumours and Fluff
From what I have been able to accertain over the years of articles, quotes, fluff pieces and such the basic story goes like this. Both men were coached by Mishin in Russian. Yags was first and was considered a prodigy. He excelled and even won his first Worlds at 18, I believe. As Plushy progressed, naturally the time that the coach needed to be split. There was a rivalry, it was very hard to take, because unlike some of the other great skating rivalries, the two trained on the same ice and Yags felt like that he needed to go elsewhere to a coach who could concentrate on him. Plushy has been attributed as saying that Yags took the easy way out, that if he were a true competitor he would tough it out in Russia. From there, the rest is history with the cold/snide remarks from one skater to the other. I am sure that though neither may "like" each other, they MUST respect each other for what their skating has meant to the other in terms of pushing them both to the limit.
As for who is right and who is wrong, I think the answer may be both. It takes a lot of chutzpah and beleif in ones abilities to be world champion, It doesn't happen to those who don't believe that THEY are the very best at what they do.