Vanakkam,
Thai buddhism is well known to mix deities from Sanatana Dharma and from Buddhism, as well as Buddha teachings and local animism.
From what I have seen, none of the Deva and Devi is mistreated, or deviated, no ritual is against common practices, and are loved and cared as much by Buddhists and Hindu alike.
I am not into the universalism stuff, but that's another debate. However, I am surprised that as Hindu you don't praise the coexistence of Dharma in harmony, peace and acceptance, and instead ou seems only to preach one way in a orthodox manner. It is not a good attitude to have to put down people's beliefs and what they do with it. This looks more like an abrahamic concept. And Hindus that practice Santana Dharma (those from India and those from the west alike) should have their minds free of these concepts.
If Sri GaneshJi is worshipped and loved in a south east asian country with a Buddhist history and a different culture than India, what is the problem. The only problem I see is intolerance toward a matter that is none of our buisness. It does not degrade Dharma in any way in the eyes of the world.
To go back to OP (farfaaaar away) I have however objection to considering christ as a prophet or Deva. This is absolutely different, too different, and mixing these two concepts can lead to deformation of original Dharma.
More than that, Sanatana Dharma is a very large umbrella that include absolutely everything and every way needed for the sincere seeker. So...Why looking elsewhere or try to forcefully mix stuff that cause strife and fights to it ?
Aum Namah Sivaya