ExP keeps teaching our son bad words

[greenkite0]

My son will be going to a Catholic nursery after preschool and my ex partner is a mad Celtic fan, he has taught our son to say up the ra. I am appalled. The kids may not understand what it means but I am just being petty in saying to not keep saying it to him?

No, you are not being unreasonable.
I guess you are in Scotland? Glasgow area?
The IRA are terrorists and so your ex p is teaching your son that terrorism is okay- would you be comfortable with a child talking about ISIS in positive terms in nursery?
He would almost certainly get in trouble and you'll be called in to explain yourself. (I am a teacher btw)
Also- if you are in Scotland, nurseries aren't 'catholic'- they may be attached to a catholic school but catholic re generally isn't covered. So you will find a nursery is a very mixed bag with religions.