Nobody should be anywhere near an active runway (unless you have permission and know what you are doing,.. i.e where to look)
Absolutely right of course, but
tearing strips of the chap..
is inappropriate.
Education is so much more effective than punishment. GA needs top recognise that it is a leisure industry & should stop treating newcomers as six year old children.
Without knowing the OP or his airfield, it's hard to judge the severity of the incident, but the fact that he's here asking questions suggests that the lesson has not been learned.
Not an effective instructor.