some instructors does it and defends themselves like "if the wings will be damaged let it happen now, the aircraft is stronger than you think",
And this coming from a "Professional Pilot"?!
Limitations are not targets, generally speaking I always try and take a few extra knots "for mum", both in my professional job and when flying the clubs PA28.
It sounds like you have a much more professional attitude than perhaps your instructor(s) do. I would suggest a discussion on the ground next time around and if they continue to fly outside the aircraft limitations a discussion with the CFI needs to take place.