where will you say "I am sorry but that is not the bible."?
Actually with believers I usually try to point out when their idea is contradicted by other scriptures or simply a theory instead of scripture, and that latter is actually why I'm in this discussion, as in earlier posts above, pointing out that presuming little or no time passed in Gen 1:1 is an assumption, not scripture.
When we have an idea that isn't scripture but instead a way of interpreting scripture and using certain assumptions, it might be ok, so long as we make clear to the people we are talking with it's only our own personal idea, though many other people have that same idea.
But if we assert our assumptions or extra ideas -- for instance the idea little or no time passed during verse 1 -- as being the Truth, when they are in fact our own ideas, that's "adding to scripture".
If we say, "My view is that ____" or any similar wording that clearly shows it's just one viewpoint among various Christian viewpoints (of real believers who take the Bible as fully true), then it doesn't have that wrong of adding (our own assumptions) to scripture.
Generally though people that preached young Earth haven't been aware they are adding a big assumption, even though they are, so I don't think they will be held to account for what they were unaware of, as we are accountable for the real contents of our hearts, not for mere honestly mistaken ideas.
But the larger problem of blocking the lost who are in some manner (some of them) interested in God enough to be in discussions with arguments about evolution is a very serious problem, which Paul showed us a better example, and also told us to be respectable, which sometimes means self-sacrifice (1rst Corinthians chapter 8) for the sake of those weaker than ourselves. In other words, you are accountable for if you block some lost seeker over the internet what what appears to that seeker false and has nothing in it of the saving gospel.
