Imus got it wrong. It’s Levin that hates Beck. (don’t know why) I can’t remember hearing Rush or Hannity talk badly about Beck - I don’t listen to Hannity that often though.
I have not heard Rush rant about Hannity, but more like dismissive of him, my take was that he considered him a nuisance. On the other hand I have yet to hear Hannity mention the name of Beck, and I am a regular watcher. I could have missed it but......