Here are your words with a couple of changes, and viewed from a Judaic perspective.....
Just because we both use the Old Testament as a reference does not mean that our G-d is the same. They believe in a distorion of what we hold to be true. They believe in a false god. Their belief is so contrary to ours that they have distorted the Judaic G-d to the point that it is no longer the Judaic G-d. Yehoshua would be a false messiah in one sense. They have hijacked a religion and a true G-d. Historically, it is the same entity that they worship. That is it. From there they have created a false religion and a god that does not exist.