A. YOU have every right to feel how YOU want to feel about the situation, No one has the right to tell YOU how YOU should feel about any situation.
The DM doing this may be a symptom and probably not the REAL problem. One of these, or a combination of these, things are the problem. You / the DM / the Group.
Sorry for the novel but it does suck when something that happens. When you have put time and effort into something and it is taken away like that it is a dick move by the DM.