Well Muslim men are only allowed to marry Muslim women, Christian or Jewish. And I suppose one of the reasons is the rituals involved, and similarities. It's not surprising for it to be overwhelming for someone outside of those religions.
No need to carry any flags. It's best to avoid going to Morocco for marriage to begin with. Many documentaries have shown what the usual outcome is for foreigners getting married to those from the developing world. Not all of them are daft enough to request money, or ask about a visa. Some of them are patient, and know how not to raise suspicions. Many people have found out only later on, what the real intention was, only after their spouse received their Indefinite Leave to Remain/Passport, and does a runner shortly afterwards. Some of them use their knowledge of their partners bank details to access money without permission.
As for older women and younger men, that's always a no-no, regardless of how long they've known each other. Simply because in the culture, men don't marry older women. Quite the opposite! There is plenty of single youngsters so there is no need at all for someone to resort to that, unless of course there is money and/or visa on offer.