Please don't take offense, but your gaming group sounds like a bunch of whiny, powergaming, min/maxing muchkins.
Don't let them push you around. It doesn't matter a darn what most other D&D players do. It is your game and you make the rules. You shouldn't change your game around just because a bunch of other guys play the game a certain way.
Now if you want to start the game off at higher levels fine, if you think it would be fun to have the PC's always get full hit dice everytime they level up that's fine too (although in my opinion, it is pretty munchkiny, and I would never do it), as long as it is a game that both you and your players can have fun playing.
In any case I would take a firm stand with them, if you have already decided that your are starting at level 1 or that they have to take their bad dice rolls then stick with your decision. Don't back down, or they will start second guessig all your rulings. As the DM you need to have authority and command respect. The worst thing that you can do is be wishy washy.
Whatever you do let your players make you their bitch.
If you care to know, I start players of at level 1 for a campaign unless there was a special reason not too, I would more likely start them off at higher levels for a 1-shot adventure if we were currently playing a low-level game or at low levels if we were in a high level campaign, just for a change of pace. And I would not mess with the die rolls.
But please, pay no attention to how I play the game.