Stating an opinion emphatically does not make it a fact. Yet, this is a popular tactic and practiced more often than not in the workplace. Those who are loud often push their ideas forward, those who have the facts feel railroaded.
Using best practices is a double edged sword. You cannot counter the loud mouths by offering a best practice. You will be out maneuvered with arguments that show the exceptions to your proposals.
Your best bet is to achieve clarity on the problem, achieve clarity on what you do not know, and reserve the right to opinion until facts are proven. Invest your time in analysis and arm yourself with the details, know your audience when you present your information. Those who understand their audience will offer the most compelling arguments. If you are not prepared, and have not done your homework, maybe the loud mouth deserves to win.