Actually, His true followers are those who obey Jesus. Unfortunately, most of us claiming to be Christians do not fall into that category and we give true Christians a bad name.
Jesus, however, IS the God of the Old Testament as well, so we cannot simply dismiss the Old Testament as inapplicable. The fact of the matter is that God often decides to weed his garden. This is not popular with weeds, but it is God's right as the gardener to do so.
True, in this phase of History, we have Jesus' command to love our enemies as part of a new Covenant with his people. But that does not mean that in prior times God did not command that many weeds be pulled up by the roots. This often includes His own disobedient people. We all start out as weeds.
I can understand why people who believe that all religions are the mere inventions of men would try to draw a moral equivalence between God's revealed Truth and all the counterfeits.
The difference is that God has the right to weed His garden and the rest of us don't.
RE: What Muslims Believe