What your asking about isn't leadership. It's more about how teams can collaboratively work best together. When I lead projects where this happens, I ask for alternatives, and encourage the debate, while reminding people of the practical limits (e.g. we can't debate forever - we have to deliver something at some point). As the lead, you have to make the final decision, but not alienate people or put them down.
I think another, really critical thing that people often forget to do, is follow up after decisions are made. Someone might have had a great idea that didn't get implemented, or an idea that maybe wasn't so good and was never considered - both of those are absolutely okay. If you follow up with the people who put the most energy into the debate (whether or not their ideas were followed), you'll find that they generally care the most about trying to solve problems. If you keep inviting those people back (even if their ideas maybe aren't the greatest), you'll get a much more diverse point of view on new problems in the future, which is way more valuable to creative thinking in an organization than picking the "winning" and "losing" ideas.
You might wonder, "Well what about the people that put little or no energy into the process?" I wouldn't worry about that either. Just make sure they know that they're welcome to speak up, and they will when they want and need to.