That was a killer statement from Rebecca, made them both look grubby and Sean, in particular, quite nasty.
If he had a shred of decency in him he would withdraw but of course he would lose money if he did which is why I think he hasn't.
I think the difference with others who have had affairs/romances and why they didn't face such opprobrium is the way they conducted themselves, none of the others had the sleazy whiff this has.
You are right Going none of those you mentioned were married - Brendan and Flavia were in long term relationships with other dancers (Brendan was engaged I think). Pascha, Kristina and Giovanni were neither married nor in long term relationships, however, their partners were. Rachel Riley was married, now divorced and with Pascha, Joe Calzaghe was in a long term relationship but apparently split up before the show and then dated Kristina afterwards, Ben Cohen was married, now divorced and married to Kristina, Georgia May Foote split with her boyfriend mid show and then went out with Giovanni for a while.
Brendan did take a fair bit of flak over the way he treated Camilla Dallerup.