[RogerL]

If you intend to emphasize the object in that first sentence, the passive voice is correct (as in this sentence). However, we usually do not want to do that. Consider:

The chair leg has been chewed by my bored dog.

vs

My bored dog chewed the chair leg.

The former, being passive, emphasizes the chair leg rather than the subject.

Anyway, a non-passive rewrite of your first sentence is: "I find that completely absurd". Note the active voice. I find it a truer representation of your thoughts. You are making a judgement on the concept, and this wording makes that clear.

[jimmaswell]

I guess I mostly prefer to emphasize the object when the actor isn't necessary. I've known the deal with the passive voice. It's better used when it makes the sentence shorter rather than longer.