2) LBS doesn't improve him/herself by ... what I see as 'lowering' oneself to invade the WAS' space
I'd like to address this point specifically.
It is not "lowering oneself" to do what is necessary to protect your family. In fact, if I may go out on a limb, if we're talking about a potentially cheating wife/betrayed husband situation, I'd go so far as to say it is the man's RESPONSIBILITY to protect his family from predators.
And make no mistake, an OP is, by definition, a PREDATOR.
Do you not protect what comes into your home? Via the television, or the internet for example? Is it "invading the space" of a teenager to check their room for drugs, if you have reason to suspect they're using them?
For the record, I am ONLY in favor of doing this where there is "probable cause," and even then, only for some finite amount of time (as outlined in my post above). I don't think, for example, that you go into your marriage monitoring your spouse's activity, all in the name of "protecting the marital home." But when you have a reasonable suspicion, based upon their behavior, possibly coupled with some prior infidelity on their part?