It depends what they are sharing. Sharing copyrighted works without the authorization of the copyright holder is the common definition of piracy. In which case, how is it unethical (as you say) to equate the two?
Because "piracy" is a slur that equates sharing to attacking ships and stealing cargo and threatening or even killing people.
The implication in copyright-infringement = piracy is that when you share something, you are an aggressor actively attacking the copyright holder. It's complete garbage and shouldn't be tolerated. Sharing is the complete opposite motivation from stealing. We want to encourage sharing and oppose stealing. Trying to equate them is ludicrous.
Of all the things to be incensed by on this topic, the fact that words have more than one definition (with the copyright infringement meaning going back to at least the 18th century[1] - it's not a recent derivation) has got to be the most bizarre. I honestly can't tell if you're joking or not.
