Of course not. Vote for whomever you want. Write in Micky Mouse if that makes you happy.
It is only Democrats in Michigan who force you to vote for a certain candidate.
If ALL Conservatives hate McCain then McCain would have lost every state. If all Republicans are Conservatives then McCain would have lost every state. The problem that you are facing is that not ALL Conservatives hate McCain and not all Republicans are Conservatives.
PS: McCain lost Michigan.