Are you kidding? That's one of my favourite pieces of profanity in the series - tony is really trying to chastise richie and, as his vocabulary is so limited, he has to resort to a frankly ludicrous emphasising of 'fuck' with 'motherfuck'. It just shows how that, at heart, tony is so much more of a thug than the dignified mobsters of 'the godfather'. You can't fault chris' inspired and fantasising language, i mean his 'two bazookas, say hello to my leetle friend' speech in season one is priceless!