We had that in the USA, Canada and other immigrant countries where people were expected to assimilate to their adoptive country culture, language but not always necessarily religion. The issue for example with the Canadians was how they tried to assimilate the native populations that existed here and what cultural, social destruction occurred due to the misguided racist attempts to stop them from being "indian" and become "Canadian" but incidentally those that came out of the program damaged and all still faced discrimination and were looked as natives just dressed as "whites" but in meantime lost connection to their culture. Leading to many social problems such as alcoholism and other problems.
The issues here in this thread is a different culture, religion moving into a region, being the minority and how they could convert the locals to their side be that language, religion, culture or all three. The problem was that even those who did convert and tried to assimilate were never treated as French citizens but always as 2nd class citizens better than the 3rd class natives but not same as true French.
I dont want to defend the conduct of the french in Algeria. This is a very delicate issue and discussing it IMO requires utmost care - something the OP absluty lacked. However the questions - why didnt France try to convert the local muslims? Could he have succeded if he tried? Would it have been possible to retain control of a part or the whole of Algeria for France if he went down this route? These I think are interesting question that I think we should be able to debate - while going out of our way to avoid any allegiations that christianity is superior to islam or being french is in any way preferable to being algerian.