If it makes them feel good about themselves, Let them do it, No one is being forced to used double eyelid tape or get surgery. Makeup makes you more confident and helps your overall mood, If this is how they chose to wear it they can do whatever they want.
First off if you’re not asian—stop. Second, double eyelid tape of good brands doesn’t inflict disease or infection. Third, allow people to do what they want. Maybe eyelid tape is comfortable for them. Maybe eyelid tape is a passageway for asian makeup artists to express in a plethora of ways. Or maybe this is a step for an Asian girl/boy/child to discover what they are comfortable with. Anyway, let them figure it out— just foster mental and physical health without harsh restrictions.
Everyone is different and you should love you for you. You shouldn't change how you look to fit in or be like everyone else. Just be yourself! And I'm not really sure if it's healthy or not, but it might make you unhappy if you do. I would say do it only if you really want to.