Not every christian believes in the absolute "being" nature of the trinity, rather than governance and purpose.

The Nicene Creed that established that aspect to the Gospel was formed hundreds of years after Apostolic Authority vanished unexpectedly, and the document and Creed itself was majory redacted and amended 56 years later to contradict massively with its former writing in 325 A.D.
So it's entiely understandable for some Christians to think that the Creed is Shokey or downright falsely established by man alone and not God.

However, because Jesus's word is so important to the will of our Heavenly Father, it's also still possible to argue that Jews and Muslims still are not worshipping "God" if they misinterpret his will so much that they shun the word of Christ.
But that depends whether the individual Christian in particular sees the other Abrahamic religions as spiteful/rebellious or just misguided; however that really ALSO depends on the individual practicioner of said other religion.
All-in-all, it boils down to: If they're a dick to your religion and the nature of good things, then they're simply a dick. Otherwise they are still a good person. Jesus himself said that in a way: Mark 9:38-40 "...we saw one casting out devils in thy name, and he followeth not us: and we forbade him, because he followeth not us. But Jesus said, Forbid him not: for there is no man which shall do a miracle in my name, that can lightly speak evil of me. For he that is not against us is on our part." As much as I dislike the King James Version the message is still there.