I suppose I don't understand the point. We know that when records do not exist in the RIGHT table that NULLs are returned. So why would we expect a filter condition on the RIGHT table to treat NULLs differently than we would otherwise?

i.e. Simply change the filter condition to account for NULLs

WHERE Professor.HasTenure = 'True'

AND (Class.ClassYear >= 2011 OR Class.ClassYear IS NULL)