The al-Fayed family were well-known in the UK long before Dodi and Diana became involved. Mohammed al-Fayed was the owner of Harrods and the owner of Fulham Football Club, as well as the Ritz. He'd been involved in some very controversial business dealings in the 1980s, and he was then involved in a political scandal in which he paid Members of Parliament to ask questions on his behalf. So there was certainly a sense that Diana had got involved with a rather dodgy family, but that was nothing to do with race: it was to do with Dodi's father's financial controversies.
True he was not a good pick. But the truth is that whoever was Dis first public romance there would have been a lot of press interest, in the UK and iwth the paparazzi from outside the UK who were even more aggressive in their tactics... If she'd been seen on holiday with an American businessman, or the Duke of Wherever, no matter where they were from, the press would have been on their tail because they'd been waiting for a year for Diana to be seen publicly with a new man. Even if the man were very dull and respectable, the press would have been all over them for a bit.