Is that really the issue? If these groups have genuine reasons to support the merger, having AT&T pay them to be vocal and even motivate their base is not a disservice to their members nor does it have any ethical implications. Although it might be hard to defend, there's nothing improper.
In my opinion, the real connection is the suspension of incredulity required to accept that they have genuine reasons to support the merger. Sans the Cattle Ranchers, these groups are typically pro regulation and watchdog large corporations for rights violations. They generally oppose large mergers because of lost jobs that they believe might unfairly target their base.
Regarding Cattle Ranchers, they usually own lots of ground and a portion of their members may actually profit from leasing ground to cell towers. The consolidation of the two companies will likely negatively affect these leases. At best, this is an extremely weak connection but it's a con, not a pro.