Neither Libya nor Egypt are parts of Europe, so they can hardly count for these Redditors' arguments.

Incidentally, during the Middle Ages the blacks in what's now southern Egypt & Sudan were Christian opponents of the Muslim Arabs, and eventually destroyed by them (and the Muslim Ottoman Turks). They certainly wouldn't have helped the latter invade other Christian kingdoms, such as Visigothic Spain or the (much closer) Byzantine Empire.

Even in the times of the Roman Empire, lighter-skinned North Africans considered themselves distinct from and looked down upon darker-skinned sub-Saharan Africans, of whom a few (so few that even many Romans-from-Africa were surprised by their existence) served in the legions. Like the Emperor Septimius Severus, an African Roman (of mixed Punic, ie. Phoenician/Lebanese + Berber, and Italic heritage hailing from modern western Libya) who saw an 'Ethiopian' (actually black) legionary and was shocked & appalled by the sight, thinking his presence to be a bad omen.