I used to hate them too, but I learnt how to deal with them.
First, never try hitting them in melee, you’ll miss, a lot. Second, throw things at them, you’re more likely to hit, or better yet, use a gun. However, my favourite method is to use the Control Laptop, turn them in to your allies, then pick them up and store them for later.
Seriously, Manhacks are so powerful, I just unleashed a swarm of 20 manhacks which then proceeded to kill over 200 zombies in the biggest horde I have ever seen, without taking ANY damage.