Fine, it's not unethical, but it's stupid. Did they think they had a shot after one run-in at a bar? Would you join another team after running into them at a bar with no knowledge of their idea?
What are you saying is stupid? Wanting him, or thinking they could get him? If you all went to undergrad together, then it's possible they know more about his talent than either of you realize. I certainly have classmates who didn't know me very well, who, while I wouldn't take them as the other half of a two-man team, I would take them as a third or fourth man give that I already had one committed partner. And while their chances at success may have been slim, it's not like the attempt required much of an investment.
It was stupid that they thought they could get him. Of course, he's good. They should have wanted him, but he also barely knew my partner during undergrad. And we were actually pretty good friends before this incident.
