Even though I hate Marcus he wasn't being racist at all, afterall he's good friends with Siavash in the house. If Karly was getting all up in face and arguing back, he would have mimicked her just the same with a scottish accent if he could do it. Similiarly, he would have mimicked Noirin's irish accent.
What is with all your Ofcom complaints anyway. You seriously need to get a life!