I'm sorry that you only see circular reasoning when debating Christianity.<quoted text>
If this was a joke, discard this response.
You need to learn what circular reasoning means. Here's an example:
1. The bible says god exists.
2. Thus god exists.
3. Thus the bible is true.
Pointing out that something is relative, in other words subjective, is not circular.
I'm sure you know, but circular reasoning is when the reasoner begins with what they are trying to end up with.
In this case, it was "ancient".
OCB & Mac's reasoning is that ancient means really old, but only as old as they deem it, to suit their argument that the crusades isn't an ancient part of our history.
So. Start with "the crusades isn't ancient" and you'll likely arrive at a definition for 'ancient' that suits the argument.