The phrase "to broaden the debate" means to expand or make the discussion more inclusive by including different viewpoints, ideas, and perspectives. Full definition
«We want to support organizations that are trying to broaden the debate on an issue that is so important to all of us,» said Tom Cirigliano, a spokesman for Exxon. (heatisonline.org)
Our article broadens these debates in two ways as I see it. (rs.resalliance.org)
With this issue we intend to broaden the debate by taking seriously the potential of non-statist political and social movements to address global injustices. (blog.politics.ox.ac.uk)