A good reason to seek out the Church that Christ founded, the "pillar and foundation of truth."
The truth is not as black or white as the Calvinist would wish it to be. We do not believe Original Sin is death, only disabling. Consequently, other cultures, including that of Islam, are operating at a great deficiency, but they are not dead or totally in the dark.
There can indeed be great "good" done by Muslims, as it can be done by Hindus or athiests.
I realize this conflicts with your Calvinism, but such is the way we view things. One can say the Koran and Islam are false paths to salvation. But one can not say that therefore the Koran contains nothing that is true, and that Muslims have accompished absoutely nothing good and decent in the attempt to follow their faith.
You will respond that all enelected men are entirely dead and that nothing that they do is pleasing to God.
I will note that the Samaritan's actions were pleasing to God, even if his attempts to follow and udnerstand God were less than perfect.
SD