You don't have to be a jerk to be a good boss. It may make you look better to upper management, but honestly, they aren't the ones you have to work with every day.
I too have often been accused of being "too nice"---I don't write people up when I suppose I should, don't yell at them for making mistakes, don't push them hard enough. Well, as someone who's had all of the above crammed down my throat at one point or another in 30+ years of working, I find that I am NOT motivated by fear and loathing........in fact, when I'm treated like something the boss just scraped off the bottom of his/her shoe, I tend to leave. So do most people who have any self-esteem at all, and the ones who don't I wouldn't really want working for me anyway.
Ironically, I probably have fewer issues with my aides (I'm a charge nurse in LTC) than the hard-liners............I rarely have problems getting them to do their work, seldom have to deal with call-ins, and almost never have trouble finding them when they are needed. All I do is treat them like adults and expect them to act that way. I always assume that a problem is FIRST one of education, not laziness, and I will teach an aide how to do the task properly or review it with them. (After that, if they still aren't "getting it" I do a verbal counseling privately with the employee, then a write-up if necessary.)
OK, so it doesn't always make the middle and upper management happy that I don't write up everyone for the smallest offense...........my ONLY concern is that the work gets done and that it's done right. It's funny, how even aides I've never worked with will beg to be assigned to my unit, but I think it's because I treat everyone respectfully and don't act like they are "beneath" me.