Most likely that line-up was already finalized in the schedule. If A&E pulled them now, they'd be extremely hard-pressed to find enough material to fill those time slots, particularly material that would draw their viewers, and would satisfy their advertisers. Most likely, if A&E pulled this line-up they'd still have to pay Gurney Productions (the entity that employs Robertson, produces the show, and sells it to A&E - almost certainly retaining a cut of the intellectual property rights), and would probably have to pay penalties to their advertisers who would have purchased air time based on the show being run.