I don't deny Bristol and Liverpool benefited, but replacing one wrong version of history with another wrong version of history isn't a step forwards.
Bristol and Liverpool were merely 'transport hubs', where what they were transporting was owned by people right around the UK. Even Bristol's most famous slaver - Edward Colston, who also was Bristol's MP - didn't live any of his adult or slave-owner life in Bristol; he lived solely in London.
(the association comes merely from him having been born in Bristol)
And while it wasn't the very poor who owned slaves, it wasn't only 'the rich' who did. Records from the compensation paid out at abolition show who the slave owners were - and* there were a lot of 'ordinary people' who owned them.
(* particularly in Scotland, where around half of the UK's slave owners lived).
Did Bristol "benefit enormously" from slavery? I'd say that proportionally the wool trading towns of a slightly earlier age got far richer from stealing the UK's land via enclosures than Bristol got from slavery.
(it's worth noting that Clifton was outside of Bristol back then. It actually came about as a place because slavers didn't want to pay Bristol's taxes - which might have had Bristol 'benefit enormously')
As for Liverpool, its riches mostly came from the post-slavery age after it had built its 'floating harbours' (Royal Albert Dock, etc).
Transport hubs generally do benefit financially though, maybe not the most, but certainly enough to be put into historical context? And Bristol got it's hall from colston!
I think teaching more about colonial past is a good thing anyway.