As a Christian, this kind of thing is so frustrating. Obviously in order to be a believer, you're going to have to hold views that may not always be popular or make sense to others. But that's YOUR burden, not everyone else's. Why Ham feels the need to take his stand here can be somewhat confusing to non-Christians and it can really only be understood when you take his particular brand of hyper-literalism into account.

His theology stands firmly on what he would call a "literalist" interpretation of the scriptures. For him the Bible is full of certainties regarding things like heaven and hell and the wrath of God (and God's goodness as well, to be fair). There is no real wiggle room. And if you were able to poke a hole in any one of those interpretations then the door would be open to poking holes in all the others. That's what he's working so feverishly to avoid. Creationism is more about preserving an entire theology and hermeneutic than it is about maintaining a theologically consistent creation account or myth.

Hopefully this helps provide a little context into why someone would stand so firmly by something many people consider so inconsequential.