Set expectation to allow all voices to be heard. What I've done is 1. Inform all participants they are given 5 minutes to think through and prepare what they want to say. 2. Provide 2 minutes for each person to articulate their point of view. A clash of opinions isn’t necessarily a negative outcome. On the contrary, it indicates active engagement and demonstrates that participants are invested in the session's discussions and outcomes.

When opinions clash it's actually good, because this is the way how the best idea can be born. The main point in this is to ensure that things don't get nasty, and for that facilitation is crucial. Setting and emphasizing ground rules and continuously showing that in the end, we all want the same thing - do our job well and achieve the best results - helps to understand that we all are on the same side. But sometimes just taking a break when things get too heated also helps. If the discussion is respectful and not getting personal, it's a good chance for something good to emerge.

Clashing of opinions happens only when everybody is participating which is a good sign. The fact that everybody is being heard happens only when people start talking openly about it. Situation gets tough when we do not come to a conclusion. Agreement might not happen every time but at times we should agree to disagree. I usually encourage short breaks if discussions become too heated. This allows participants to cool off and collect their thoughts. Also its good to promote the idea that it is okay to disagree as long as it is done respectfully.

Clear expectations about mutual respect, what is allowed and what isn't and the consequences of being disrespectful. Also you might want to remind people that everyone has an opinion (on everything) and just because you think you are right doesn't stop others from also thinking they are right. It's ok to disagree, respectfully with intelligent arguments.