A sketch represents a particular solution for the user needs in a given context. People unaware of such context will provide feedback based on their personal opinions or the scenarios that they imagine. You need to move the conversation from what people like about a drawing to what they expect to work--or not--for the users, in the presented idea.

You need to make a constant effort to connect the discussion with the goals. As mentioned for the critique sessions, it is important to introduce the goals before you present a solution. In addition, you need to be careful to keep the conversation connected to those goals when you describe the solution and receive feedback.

Avoid presenting your solution by just describing its parts. If you just describe individual pieces, it will be hard for the audience to understand the role those pieces have in supporting the user needs. Instead of saying "here is the search bar", you can indicate that "since data shows that searching is the most common activity for our users, we provided a quick way to search".

Even if you make an effort to present the context of your design connected to the goals, you may still get feedback that is too specific or based on personal opinions. In those cases, you need to reinterpret the specific feedback that people provide.

When anyone in your team asks for a specific change in the designs--such as adding an icon to that button--you need to understand the underlying issues that the suggestion is trying to address. By asking in which way that change is going to help the user achieve their goals, you can separate the proposed solution from the underlying issue in a better way, which can potentially be better solved with other alternative solutions.

You need to make sure that you do not discourage a person from asking. You don't want them to feel they are asking stupid questions since that will demotivate them from providing more feedback in the future. You want to express your honest interest in learning more about the root cause of their concern.