Dear (billable by the hour) consultant-
You are brought in to help us find a solution. You are not to bring the one solution that you know and try to fit us in there. You are to find a solution that fits the client, not a client that fits the solution. So next time please present at least two different solutions (see here why), otherwise we are going to bill you for our time instead.
[ Inspired by discussions with colleagues from both the private and public sector ]
Managing organized complexity 
It all boils down to shoddy recruiting purposes. “One hammer to rule all them nails” consultants are easy to spot during the interview phase. Of course, if the consultant (or more likely the company/agency behind him) is “forced in”, then you have my sincere sympathies