You're trying to make a false distinction between small immoralities and big immoralities. If Google is doing something immoral with respect to its employees, the fact that those employees can depart is irrelevant. Employee freedom does not neutralize employer immoralities, no matter what the size of those immoralities.
Now, if you want to argue that what Google is doing is not immoral, then fair enough. I might even agree with you. But if we're taking it as a given that this action is wrong, then employee freedom doesn't make it right.
Exposing someone to danger because you're too cheap to pay for proper safety is what I'd consider immoral.
Not offering employees a certain class of shares is maybe lame, but not in the slightest what I consider immoral.
We're not talking about inhumane working conditions here, backbreaking labor, or an employer risking people's lives to make some extra bucks.