why does everyone hate zbt??

The first rush event I went to was at ZBT and I thought the guys were really cool, and their house is amazing. However I've seen a lot of hate on here about ZBT and was wondering why? The first event I went to I met a lot of the brothers but I did see some of the brother's shaking each other's hand thinking the other was a rushee. It's like they never met before! Also I got a bid after that first event, and they told me I could become a brother by next weekend if I accept. I was told they have functions with A Phi, Kappa, and Chi O pretty much every weekend, so why all the hate???