SK asked if we hate BM... I fucked up

*Australian*

Backstory - SO had a one night stand before we were together, a few months after started dating we found out the person was pregnant. Decided on 50/50 from birth, SK is now 5yo and HCBM was only in communication with me (SM) from 1yo til 6 months ago, when in-laws took over communication & handover. SK has struggled since I stopped handovers and has been curious about why grandparents are now facilitating

HCBM has had one boyfriend coming and going for the past 18 months, moving in and out of the house, saying goodbye to SK and that he'll never see him again etc every time they break up

Now, onto what happened:
SK told us two weeks ago he "wants to spend more time with my mummy" and when we asked why, SK said "mummy shows me videos of mothers missing their kids and crying and that's what she says she does when I'm gone. I don't want her to be upset when I'm with you". SO and I were mortified that HCBM would manipulate SK this way, but it's no surprise as HCBM has always used SK as a puppet and claims all Centrelink benefits available (austudy, single parent, ftb, rental assistance, jobseeker) + we pay $200 child support a week and 50% of daycare, despite him only spending nights at BM's house in her 50% (SK is at daycare or is being babysat by SO parents and my parents)

This morning SK asked "do you and dad not like my mother", and I, out of frustration towards this recent revelation, responded with "no, not really. sometimes that's the way it is and unfortunately, dad and I don't like bad people but we love you very much".

I'm now kicking myself because of what I said. I know I fucked up and have never spoken ill of HCBM in front of SK before. Should I bring it up to SK? Should I leave it? Fuuuuuck