You're probably too young to have had many people treat your hard work and money with disrespect. You'll think about it differently further down the track when you learn that it's worth trying to do the right thing when you can.
Nobody disrespected anyone, that's just business sometimes you lose, sometimes you win, which ever side your on you just keep going. No right or wrong here, if it was that case always do the right thing, in this case the other business just lost talent, they wanna compete they can by offering or matching it.
Just business.
Many people think that it costs nothing to anyone to recruit a person into a job. I think the recruiter would not agree with "no right or wrong" - they put in the effort to find this guy, shepherd him through the recruitment process, is now not getting paid and has missed the chance to put someone else into the job who would have stayed. I suspect that recruiter might feel somewhat less circumspect about the outcome.