There are numerous scenarios where in-house creatives find themselves having to manage difficult and even reasonable clients. If this is occurring in your team on a frequent basis you need to end the practice or train up your creatives in client management techniques ASAP. Otherwise admit that you are knowingly tolerating a major dysfunction in your group that is negatively impacting morale and performance. It’s unfair, unethical and is an illustration of management incompetence.
While regular interaction with clients is a common and reasonable expectation of in-house designers, writers and others with creative roles in corporate creative teams (moreso than in the agency and design firm world where creatives are physically and often organizationally separated from clients by being off site and having account management teams respectively) there should be limits to the types of interactions your teams have with their clients. Healthy and sustainable creative/client relationships are characterized by the exchange of information relevant to the project at hand. These types of communications include initial direction (effective creative briefs), objective feedback, scheduling and even brainstorming. Scope creep, arbitrary subjective creative direction, unreasonable demands, pushback on client deliverables and responsibilities are exchanges that should not fall on the shoulders of creatives to handle.
The most effective way to manage client management is to create an account management team. If this is not an option and your team and its client base are small enough, as manager of the team, you should take on this role. As a last resort, if your creatives have to assume the role of managing your clients, then at the very least, you should provide training and coaching to them on the relevant skill sets.
Nothing will erode morale, distract your teams from there core responsibilities, escalate attrition and severely impact the productivity and creativity of your creatives more than a failure to address the issue of client management.