Employees complaining about upper management? Best way to navigate this?

I started at a company a little under a month ago, and manage a small team of three. The team for the most part has been great. The one thing that worries me is the employees are considerably unhappy with the conduct of one of the senior managers training me. They have detailed condescending behavior towards my employees. I observe and acknowledge it myself, but I don't know the best way to handle it without stepping on any toes being so new with this company. How can I stand up for my employees without stepping on toes or worrying about retaliation?