The exclusivity of Christ as the only way to God is not a claim made by Christians about Jesus — it is a claim Jesus made about Himself. In John 14:6, Jesus makes three absolute declarations: He is the way (not a way among many), the truth (not one perspective among many), and the life (not one source of spiritual vitality among many). The definite article "the" is crucial — it is singular, exclusive, and allows no alternatives.
Jesus further stated, "I am the door: by me if any man enter in, he shall be saved" (John 10:9). He did not say He was a door. He said He was the door. He also declared, "He that believeth on the Son hath everlasting life: and he that believeth not the Son shall not see life; but the wrath of God abideth on him" (John 3:36). There are only two categories of people in God's economy: those who believe in Jesus and have eternal life, and those who do not believe and face God's wrath.
Modern culture calls this narrow and intolerant. But Jesus Himself said, "Enter ye in at the strait gate: for wide is the gate, and broad is the way, that leadeth to destruction, and many there be which go in thereat: Because strait is the gate, and narrow is the way, which leadeth unto life, and few there be that find it" (Matthew 7:13-14). Truth, by its very nature, is exclusive. Two plus two equals four — that excludes every other answer. Jesus is the way — that excludes every other way.