This phrase is the distinctive marker of a disclaimer which usually precedes, or occasionally follows, a positive or negative criticism.

Far be it from me to impose my opinions on anyone else, but I think that that is just sick!

Its claim is usually directly contradicted upon completion of the thought.

What he is doing is sick! Although, far be it from me to suggest that I am a better person than he is.

The level of contradiction can be a matter of degree.

Far be it from me to claim to know everything, but I know sick when I see it!

Some people use it and are apparently unaware that they have seeded their statement with irony. However, many people use it as a backhanded way of saying exactly what they claim to be disclaiming.

But far be it from me to make any assumptions about the usage of the phrase.

I am, however, sick.