Ah, well if you’re competing for the same territory that’s different.
You’re equals in that case and it’s not master/student anymore.
In short, it sounds like you got used for their gain. Your compassion was used against you in the end, a betrayal of confidence and trust and respect.
Master level has nothing to do with age: it’s approach towards the student. They’re never your competition, even when they compete against you. They may see YOU as equal and they can do that.
But the moment you see THEM as equal, or treat them as equal, there’s no more master/student.
In the business world, for example, there’s a ‘thing’ about that: “Never tell them everything you know” because when you do, it will get used against you.
That’s because in business, there is no master/student. It’s a level playing field of opportunity for all, which is one of the things that can make it vicious.