Seriously - check the fitting. If it says that it's double insulated, or has a symbol of two squares, one inside the other, not only does it not need an earth, it must not be earthed.
Your retired electrician friend has given you dangerously inaccurate general advice that does not apply to all metal light fittings.
If there is no indication that it is double insulated, and it has earth terminal, then yes it must be earthed.
If there is no indication that it is double insulated, and it has no earth terminal, then don't use it.
Is it new, and CE marked?