Re: "If you got nothing to hide, why hide and destroy things?"
If you only hide and destroy things that are not prohibited, then who cares? [to match your rhetorical with mine]
The answer to yours is: because they were faced with an adversary that would sieze on anything that might suggest evidence of WMD in order to justify a war. Best to remove anything that might be construed as a suggestion of evidence, no? Wouldn't you?