An argument often used against Christianity is that, since Jesus is the only “Name by which men are Saved”, people who never hear about Jesus must go to Hell, and on that basis Christianity is unfair. However, Paul makes clear in Romans the role conscience plays in guiding our behaviour. This is not as great a means of Salvation as that which comes through Jesus, since there is no benefit in this life, only in the next. But it is, never the less, a clear route to Salvation.
The anti-Christian argument put forward on this “Jesus Only” basis misses its mark, apart from the reason given above, because by definition it is put forward by those who have heard about Jesus. What they are doing is citing an alleged injustice against people they do not even know, in order to justify their own rejection of Christ. It is a classic piece of anti-Christian rhetoric based on ignorance of the Bible.
Just to be clear, there is no justification in this for following conscience rather than Jesus. The conscience route exists for people with no knowledge of Jesus. Those who know about Jesus but reject Him in favour of their own conscience are making a fatal error.