I do agree that it is a sensible way to learn, just that they shouldn't take credit for it. I totally don't mind poking into stuff, it just means the original work is awesome and there're stuff to learn from it. However, there's always been the problem of taking credit away from the original creators, acting like its all yours to begin with.
I did have a friend wanting to jump into programming and came asking for advice. Later came back with a website copied and edited from another friend's website, proud.
Some people just don't understand how much time and love is poured into the design and code. Being inspired by something/someone doesn't mean you can just imitate.
Don't give up! Really admire how you kept things calm and clean.