LimeWire pro linking to bitzi spyware

[Somethingelse]

I just paid for Limewire pro from http://www.limewire.com/english/content/home.shtml

my PC has never had a virus,Trojan or running spyware in over 2 years
but within a week of getting LMpro i have had a Trojan try to run
and spyware running on my PC

LM gives you a option to "Look up a file using Bitzi"
on the site that LM sends you to
there is a tool called Bitzi for making your own sigs for your files
it's bc-setup-0.6.0 and is a install file

After installing the Bitzi, i restated and norton popped up and stopped Trojan.Dropper from running
the trojan file was iun6002.exe

I then did a full scan with ad-aware se and it found spyware (scumware) called Ezula on my PC
using ad-aware i found out that it was connected to Bitzi
i removed it and did a full scan, it came up clean
so i uninstalled Bitzi (bc-setup-0.6.0) then did a scan
and it was back!
it seems it reinstalls its self when bitzi is uninstalled
when i completely removed bitzi the PC was clean

Now LMpro wont run, its blank

Why do the makers of Limewire pro link to, and let you install spyware?