At 3 yrs old, the "<insert profanity>" has got to go. The profanity is your issue... not the sippy cup. Here you have got to make it clear that he should not repeat that word. If he should do so again... the sippy cup goes in the garbage.
Otherwise, I don't believe the sippy cup is a comfort so much as he may simply feel that he has more control getting whatever he's drinking into his mouth better when he uses a sippy cup.
At 3, it is perfectly fine for him to still use this kind of cup. Take comfort in knowing that he knows how to use a regular cup. Do not make an issue of him getting rid of the sippy cup at this age. In fact, do not "sweat" the sipping cup as that is something any kid will drop when he or she is ready.
My daughter is 4. She knows how to use a regular cup and glass. However, it gives me more comfort in knowing that 1. she an avid water drinker so I keep a spill proof cup filled regularly throughout the day, and 2, I don't worry about spills when she moves around the house with it during the day. 3 -- most important... I don't have to get up during the night as she knows where to find her water during the night -- In the corner of her bed (she drinksd, put it right back and goes back to sleep).
Nor, was I embarrassed to take this spill proof cup of water out of my pocket book in a room full of parents and other 4 yr olds 2 weeks ago during Pre-K registration.