The temple authorities are bound to obey the rules in place. But it is high time that it be revised.
To claim that entry of non Hindu is an insult to the diety is something which even Krishna would refuse. Such narrow minded thoughts should be done away with it, and all devoteees should be allowed access, just like "all" Hindus have the priviledge.
The temple authories may have a problem with foreigners entering the temple just to have a look at the antique idol, but that does not justify the insult which a person faces when refused in purely due to his religion. Such narrow minded actions would do harm to the loving lords image.