He doesn't want to darn it! What do I need to do, complete a few quests to raise my reputation?

Raising your reputation may help but if your character is of evil alingment I believe Kiven is just one of those NPC's that alingment does matter.

Dialogue reaction is determined by Reputation and Charisma. That's why Imoen has 16 CHA, so even if you screw up and kill an innocent early in the game, she can still sweet-talk all the other NPCs into joining you.

In my Evil game, I kept my Rep. pretty low (Not THAT low, but low), with Kagain as my Tank. We breeze through BG city SW, and we stop by for a chat with Tiax, just to see how he's doin'......and he wouldn't speak to us! The combination of Kagain's low CHA and the team's low Rep. was sufficient to make Tiax, TIAX of all people, refuse to have anything to do with us! Of course, my PC (Cleric/Mage with 19 CHA) got him to open up, though.

minsc also wont join your party if you are evil align. But I cant really see why anyone would want him.

You're right...the only reason someone would want Minsc is for Boo. He's better than a blindness spell.