The Pact of Umar would like to have a word with you. The Copts exist today and their rights preserved because of the Muslims protecting them. "Slaughtering" people indiscriminately like you're implying is against Islam.
https://en.wikipedia.org/wiki/Pact_of_Umar#Content
Very clearly establishing non-Muslims as second class people, with all kinds of onerous limitations on their everyday life.
Calling this pact "protection" is technically correct, but then, the Protectorate of Bohemia and Moravia in WWII was a Protectorate as well.
I would call this document "subjugation of unbelievers who serve as your tax base, so it doesn't make much sense to kill them outright".
The Copts exist today because of the Muslims, this is a fact, even if you try to twist the meaning of what I wrote. They are to be treated well, and with dignity, and their rights preserved.
Secondly, I don't see what makes them "second class citizens", not to mention that even wikipedia acknowledges discrepancies in the points they mention.
As a matter of fact, several Jewish and Christian historians and figures clearly expressed that they would rather live under a proper Islamic rule as it offers them better quality of life compared to secular modernity: https://www.youtube.com/watch?v=Bc6yXYR01Vg&t=6s