Answer: Not as a rule.
Granted, lying to investigators is not "per se" okay. You are still avoiding the question of whether (if he did) Libby can be excused, under the circumstances.
Excused by who? By me? I guess Bush could pardon Libby. I guess I could excuse Libby if I felt he was unfairly convicted.
If Libby knowingly lied and obstructed and is convicted then he deserves what he gets.