I was told to not ask if people wanted to wasp dupes?

A user traded with me when I send “Dupe swap? 🍻” and proceeded to block me I guess? Went into this whole diatribe about how it’s rude and people keep dupes for sets.

Mind you, I’m just trying to be friendly and finish sets. I usually am met with, “Sure/Thanks,” but is this seen as rude in the community? I don’t want to put the screenshot up or their username but that just doesn’t fit my usual trade activity. Am I offending people by asking if they want to swap dupes?