So, why the heck didn't Yevon use Vegnagun against Sin...in 1000 years no one thought "Ok fine, let's just give it a go, what's the worst that could happen"?

I know they say that it can't tell friend from foe when activated, but why not just do an operation Mi'ihen style thing, and stick Vegnagun infront of Sin and turn it on. Even if it didn't win, at least they gave it a try. Even if it did win, I'm sure it would be damaged enough for the rest of the Mi'ihen troops to destroy it.

So, thoughts on why no genius even thunk of the plan?