Is there ever a situation where ignorance should be respected?

I’m not talking about “ignorance is bliss”. That may or may not be so. Whether it’s bliss or burden, is there any reason to respect ignorance?

What about willful ignorance… for example, a friend wants to tell me details about how he cheated on his wife. I said “I don’t want to know”, and he was offended because he feels that he should be able to talk with his friend about anything.

I say, “Nope, because when she finds out (and she will) then you won’t be able to suspect me as the one who told her. You’ll have to accept the consequences of your actions without me to share the blame with.”

Should my position of willful ignorance be respected, or should it be discouraged?
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Another kind of ignorance is unqualified assumption. My client assumes that he owns the rights of my photography just because he paid for the shoot. I respect his ignorance, and set upon a tactful plan to educate him about how the photo business actually works, separating shoot fees from usage rights fees.