Sorry to hear this. I think it depends on the player. Some people consider a challenge to be 2 games, one as black and one as white, which is reasonable as white starts with an advantage. They expect a rematch. Others consider a challenge as one game and may set the black/white choice to random so its luck on who gets the advantage. They dont expect a rematch but might request one. I'm the latter. If a player lost due to a mistake but feels they are the better player they may request a rematch to recover points. It's an issue of expectation. IMO players are not entitled to a rematch and should not expect it. They certainly should not be rude if a request is declined. I mainly play Daily where rematch requests are relatively rare, I think I've had one in 30 games, for many people its not an issue.
Rematch offers are rude??
On the second question. I mainly play daily because I dont have much time for other formats. Despite the flexibility of the Daily games I will decline rematches if I'm generally very busy. If a game ends on sunday evening and my opponent requests a rematch, I will decline it if I know I've got a busy week ahead or pressing deadlines at work. Chess is great but it's only a game and I think some players forget this.
I generally reject the rematch offer after i win..... and accept the rematch offer after i lose...
Sorry about the insults. I dont think there is much you can do. You can probably report them but even if they are banned they can just create new accounts. They are probably young and definitely immature. They'll grow up in 10 years!
with a lot of people's mind when win it considerd us a better Player then the very opponent so we dont want to take risks to play again to might be lost.....same happen when we lose we want to equalize our defeat
I always accept rematches and always offer them despite the negative or positive result. Rematches makes things more personally, and often leads to several games, which I think is great, giving more emotions to the games because of the rivalry. 
igor great warrior i am sure, but i tell igor he even greater with pen than with sword and spear and even knife.
Nonetheless, if people would rather play matches or mini-matches, maybe there should be an option on this site to do so. My guess is that the folks who repetitively request rematches and throw insults to decliners are the type of players that will not want to ever play matches (except against much lower rated players), because they fear the uncertainty of whether they will win and fear a possible +0 =0 -6 result showing up under their profile. But after a single game ... well, you can always request a rematch.
Hi