Twitches are not evil if used correctly! They actually have a calming effect on many horses (well not my filly, but that's because she's a weirdo) which usually helps for what you are twitching them for. You shouldn't twitch a horse inappropriately or who doesn't need it, but otherwise they tend to be a very effective tool in handling a 1000lbs of pure muscle.
My filly doesn't clip, but not for lack of trying. For a month, I would bring the clippers out every day and turn them on and treat her with food if she let me get close to her. She broke about three cross ties and two or three stall corner ties. She would just have enough at some point (without much warning) and lean back on the cross ties (or corner tie) until one or both popped out. We thought she came without even being introduced to clippers, but we found out that she saw them regularly and was okay with them.. So we decided to twitch her (after literally a month of no improvement? why waste time treading water?). She was clearly scared, but let us touch her neck with the clippers turned on, when we tried to touch her muzzle she reared. We haven't tried anything since.. but I think we're going to try to put a blanket on backwards so she can't rear. If not we'll have to sedate her, since she must clip. (She's a future show horse)
Since that day, she took rearing up as a habit she did to try and intimidate me. what a witch, right? =p
She also does plenty of other naughty things my gelding wouldn't dream of doing.
Part of the problem is I don't know her well enough yet, I don't trust her, and I haven't bonded with her. She feels the same about me, so why should she let me clip her?
My gelding on the other hand, I know everything about him, I trust him with my life, and I've got an incredible bond with him, he'd follow me off a cliff if I asked him to. =]