I have seen some good and bad advice on this subject. I would tend to agree that you should talk to the GM. It almost sounds like you worked yourself into a frenzy. I agree with the comment that GMing is hard, especially with Paladin PCs. A few solutions present themselves that may help both you and your GM.
Provide a code. Most people who play Paladins assume that the GM knows exactly how they will act. Paladins can be different from the standard norm and your Paladin seems very different than a normal Paladin. Write your Code and give it to the GM. If he knows exactly what you believe, then he will know how to mold the situations in the campaign.
Unlike others, I would tend to shy away from bad-mouthing someone that I have never met. After all, we're getting one side of the story here. However, it makes sense to talk to the guy and get his opinion on the matter. Is he open to discussion? have you discussed things with him before? It make be that he had a bad day or got caught in the moment. I would discuss things with him calmly and rationally. If take him on when you're still angry, then you may put him on the defensive and that could be bad for the both of you.
Discuss things with the group. You said the NPCs were insulting? How was the group reacting? Were they defending you? Were they going along with the insults? If the latter, then the GM may have been involved in some friendly ribbing. If the other PCs were defending you, then the guy may have a problem. However, it could be a combination of both of you. Maybe you take your character too seriously, while he does not take it seriously enough. Both could cause problems.
Does he insult your character often? Does he insult you on a regular basis? Does he make fun of your personally outside of the game? It's important to find out if he acts that way all the time. If he does, then leave the game, because he will never stop.
However, you mentioned that he publicly stated concerns. That sound like he threw something out for discussion. That was the statement that made me think you let things boil up. If he states his concerns publicly, then he may be open for discussion. Most GMs I know who do this are concerned enough about the game to want feedback.
Finally, does the group insult NPCs? This could be a backlash from their previous dealings with those people. Also, as a Paladin, do you actively seek to stop your comrades from insulting NPCs. If not, then he may see no reason not to throw insults back. As a Paladin, you should protect other peoples honor just like your own. If your party dishonors people, then people will insult them and you just for association. One way to prevent this would be to step in when the party is doing something that would insult/dishonor a NPC.
You should support your GM. If he has stated concerns about PCs being insulting, then as a Paladin, you should stamp that out. That is a way for you to solve a problem in-game and support the GM at the same time. The GM can only do some much as one person against a group.
If you never support your GM publically, then it becomes players versus GM and he may feel overwhelmed. He is a member of the group too and you should treat him with respect, just as you want him to treat you with respect. If all the players oppose him, then it becomes hard to feel as if he is an equal or the servant of the party.
Some thoughts from someone who has been there.
Bolo's rock!