I think this verse sums up the discussion, at least in my eyes -
John 14:6 "Jesus saith unto him, I am the way, the truth and the life: no man cometh unto the Father, but by me."
Regardless of what name they use to call God, they must recognize that they can only be accepted by God through Jesus, who is the way, the TRUTH and the life. It is the name of Jesus that matters.
A Muslim who believes in Allah will not attain salvation, until he accepts that it is through JESUS, who is the way, the truth, and the life, and by his faith in Jesus will he be accepted by the Father.
Philippians 2:10 "That at the NAME OF JESUS every knee should bow, of things in heaven, and things in earth, and things under the earth; and that every tongue should confess that Jesus Christ is Lord, to the glory of God the Father."