We have many "inconvenient" sayings of Jesus.  This saying was based on the fact that divorced women had next to no options after their husband kicked them out of the house.  Most divorced women had no means to support themselves EXCEPT to go into prostitution.  But too many people, who don't study the social history of the times [which also shaped the writing of scripture], don't seem to understand that the official church taught many addenda to the Divine Teachings.  The Church permitted folks to kill, to steal, to lie [it all just depended on the circumstances].  

How has Newt Gingrich [now a Trump ally], been able to break up with his first wife [while she was being treated for cancer] and while married to his second wife---had an affair for eight years with Callista Bisek, a devout Catholic, before marrying her in church?  Now she is about o take up the post of Trump's new ambassador to the Vatican.  Not to be outdone, Steven Bannon divorced all of his three wives as well.