Whilst you may be tecnically correct, and I know what you mean, it is a bit of an excuse to say that because some people do bad things they cannot be what they (probably) profess to be.
There seem to be a lot of priests who are not christian, then. Bit of a disqualifier for the job, isn't it?
Also, they are not sacked when found out, so ...
Is anyone who disobeys their religion's rules therefore not - christian, muslim, whatever?
Is any one who now disregards the nasty bits of their religion not really of that religion?
IRA not christian, Protestant extremists not christian - I think they would disagree.