Nobody is a apolitical...they should not sacrifice good military judgment to carry out poorly formed strategy. Speaking to Rolling Stone was probably not the best idea.
...They are not supposed to have political allegiance to the Pres.
Their allegiance needs to be the constitution. A lot of people sight to the fact that the President can give an unlawful order (as can anyone in the chain of command).
That said, I am not a fan of some of the decisions McChrystal has made (discouraging the use of flack jackets by our troops in civilian populations, for example).