This would swing the balance too far in favor of the deletionists. The unsourced statement would have to be unreasonable. Obvious common knowledge statements should not have to be sourced, and someone edit warring, demanding that every petty statement be sourced is being unreasonable, and should not be rewarded by being allowed to impose a burden upon other editors.
Oh, I don't know - we managed to find a source for the statement "the Earth is round" :)
What a waste of time though, if you would rather have been making other contributions. -- Silverback