Ideological Hijacking of Projects
Every member in a project asserts his ideas, designs and strategies. Ideological hijacks happen when a project is steered away from your vision to others' visions. These hijacks aren't hostile as they are intended to be in the best interest of the project, and this makes it nonsensical to block, disallow or disregard others' views. Doing so also infers that you know it all and nobody can better you — even for a moment, which is completely false and dictatorial in nature.
So, you can't block such influences, but also need to ensure that they do not hijack the project ideologically and transform it to something else from what you envisioned. A solution is to create what I call as a channel of considerations that are bound by certain non-negotiable values such as ethics, project's mission, philosophy of design, financial goals and other factors. This channel will preserve the original mission of the project.
Now, every idea, design and strategy can be tested within this channel, and those that doesn't fit it can be discarded on the ground that it changes the very character of the project, and those that fit in can be considered for implementation.
To visualise this channel, think of a straight line as your original path for the project.
The various visions of your peers will form different paths, diverging from yours.
To accommodate them without straying away from the laid course, use the non-negotiable values to create a virtual channel that acts as a direction guide. Now, each time an idea tends to be so wild, alien and divergent, and crosses the limits set by these factors, even if it is your own idea, you know that you have to either dump the idea or swerve it to fall within the permissible room.