Your opponent is showing some bad sportsmanship I'd say. Just mate him.
Is it rude to reject a draw offer?

Obviously not. Really, the person who is offering the draw in the clearly losing position is the one being rude.
How could you even consider that question?

Sometimes the offer of a draw in a game with great disparity is reasonable. For example, if the side with the great material advantage has so little time left that executing the win is doubtful. However, in that case, it is usually THAT player who offers the draw and the materially-deficient side which accepts with gratitude.
Absent such compensation, if you will, an offer of a draw by a player in an absolutely losing position stems from either his/her game etiquette ignorance or downright rudeness. I don't see a lot of other options for describing it.

yes it is. in fact, i think i'm going to change the code so that when your opponent offers you a draw, you automatically accept it. that way we don't hurt anyone's feelings. thanks for bringing this to my attention!

It depends what position the game is in...if as you say the game had two more moves left to play he was probably just being rude! If you are winning by a pawn or a minor piece he could think he still has a chance offer a draw before he is completely smashed! I have offered draws when I am down by a pawn...Yes most will not accept it (especially not if their rating is higher than mine!) Also if I know them personally I will sometimes offer a draw one move before a checkmate! BUT! this is done as a joke!

It depends what position the game is in...if as you say the game had two more moves left to play he was probably just being rude! If you are winning by a pawn or a minor piece he could think he still has a chance offer a draw before he is completely smashed! I have offered draws when I am down by a pawn...Yes most will not accept it (especially not if their rating is higher than mine!) Also if I know them personally I will sometimes offer a draw one move before a checkmate! BUT! this is done as a joke!
I doubt anybody really finds that joke funny. Why not just resign, takes the same effort.

Your opponent is the one being rude. If you have a forced win in two moves then the gracious thing is for the other player to resign.

yes it is. in fact, i think i'm going to change the code so that when your opponent offers you a draw, you automatically accept it. that way we don't hurt anyone's feelings. thanks for bringing this to my attention!
Do you realise the amount of "spammablility" that has? If your opponent has a mate in 1... offer a draw!

I always have conditionals attached to my draw offer:
Once I offered someone a premium membership and a draw.

Obviously not. Really, the person who is offering the draw in the clearly losing position is the one being rude.
How could you even consider that question?
Absolutely right.
Here I am waiting for my oppoenent's move for two days and just an hour ago I saw that he had offered a draw that i rejected straight away.
http://www.chess.com/echess/game.html?id=23336346
Had he offered a draw two moves ago I would not consider it rude but at this point he should have not asked for a draw............. I think my Opponent has been rude.
I once had the temerity to offer a master a draw in a bishop-of-opposite-color endgame in which I was a pawn down. He let me know in no uncertain terms what a breach of etiquette this was and proceeded to school me a lesson in endgame play as my king and bishop defended opposite wings, it turning out that they each had chosen the wrong direction and should have been on the reverse wings for the draw. Since then I will NEVER offer a draw unless I am ahead in material, even if I can foresee a drawing sequence of moves. I leave the offer to the superior side.
I have played games in which I am clearly winning (not often, but it happens
) and my opponent offers a draw. In one case, I clearly had a mate in two moves when my oponent offered a draw.
Am I rude to reject their draw offer?