What valid reasons? I’m yet to hear any that make this mess worthwhile. The ones i’ve heard are all based on fear mongering.
Look up posted workers directive.
Corbyn gave a speech on it this week
The re flagging of ships to Malta and its effect on the labour market, if you from Liverpool look up the company that runs the ferry to Ireland for reference to how that works in practice.
The treatment of the working class on Greece, Spain ect
There are many reasons , but as you have said you haven't heard any there are a few
I don't like.
None on there own that maybe worth leaving over, but part of bigger picture to myself
It really wouldn't matter how many I put down as we have different views , but thought it good manners to reply as it seemed be frustrating you.
Look up the Laval and rufferd rulings from the EU courts might be spelled wrong as I am dyslexic.but Google will get you there.