Ok, lets try to break this down :
1. Acceptable -
They cut it to become acceptable? Acceptable to who...the rest of society? What about working and becoming acceptable to the people that brought them into this world..ie, parents. Tell them acceptability in society continually changes, but parents will always accept their child as long as he does good.
2 - Attractive.
Who are they attempting to look attractive for? Girls that go to clubs, is that the type of girl they want? One who chooses to be and sleep with numerous amounts of men, and one that can not look beyond the physical attributes? Or do they not want a girl who is moralful and aware of various teachings and knows what to really strive and look for in the world.
Tell them how much they hurt you, and how their new acceptability and attractiveness will only last with fashion, which changes every 3 years...so they must be prepared to live their life in uselessness and change rapidly. Is that the life they wish to lead?
If they still do not mind, attempt to teach them sikh history again.
If they still do not care after that...I'd say its over.