This is based on professional experience in different situations, and this is especially true when on meetings which involves more than you and the other side. Although, even some managers are very self-confident or at this point, you can say they are totally stubborn about their own ideas. The defensive systems for those personalities are so easily triggered by the least of a criticism for their actions.
The proposed solution I approached for working around this challenge while maintain the liberty of my ideas is to prepare questions which externally interrogates the details, and the consequences of a decision, and internally challenges the success and the validity of the core idea. I know that looks confusing at first; however, by comparison to the straightforward method of revealing your point of directly reveal the points of criticism, you will discover that it deserves the effort.
During one of our staff meetings for one of my employers, staff at different levels were invited to get buy-in for a new project to be implemented. The project itself looks appealing, and the CSF (Critical Success Factors) were neatly presented; however, it lacks a very important aspect of laying out a baseline for several metrics to be able to later on measure its success. This same point got my attention as well as another colleague, who had an earlier opportunity than me to take the floor. He started his words by interrogating about the current state before the project implementation and how this project might not introduce a value at all. Of course, the manager was surprised with the question and she pointed him to the clear project objectives and started over listing the benefits for this project. On my turn, I started by valuing the CSF and showed my interest to have an overview about the current baseline and the other metrics which are in place to make sure that this project is going towards success. The manager gratefully welcomed my questions and she reworded it in her own words, then asked her assistant to note it. Although I did not get an answer up till now, but I succeed in the first place to draw the attention of everyone to the value of my point, without at the same time challenging the efforts this manager and other stakeholders are putting in this project.