I would like to get your opinion on this part. Do you consider this unethical behaviour? At first it looks like it is unethical but on the other hand: while the beads might not have been worth much to Europeans themselves, they could still serve as bartering objects among natives where they were rare, "uncopyable" and therefore could serve as store of value.
Maybe this perspective helps: if aliens arrived that could effortlessly solve cryptographic puzzles (think "crypto-currency mining") and there were humans who were very interested in these - should an alien refuse to trade with a human who wanted to give them things in return for a funny number?
(If there are flaws in this comparison, point them out, please)