Dear god.
To start with, you claimed referencing other areas of parenting wasn't whataboutery - when it very clearly is. Other aspects of parenting are nothing to do with ear piercing at all and whataboutery isn't helpful to any discussion.
Secondly, the dictionary definition of mutilation is "to injure, disfigure, or make imperfect by removing or irreparably damaging parts" - which pretty much nails the definition of piercing a child's ears.
Is it a bit excessive to describe it as mutilation? Yes, probably. But then I think it's a bit excessive to puncture holes in a small child's ears.
The parenting board is supportive but that doesn't mean you turn a blind eye when asked an opinion on things which the vast majority of people would consider to be harmful, abusive, or in any other way damaging to the child. And the vast majority of people do share that view in the UK, as can be seen from the comments here.
And it's rather ironic that you talk about being supportive of parents when you're the one who's been derogatory about parents who shout at their children.
Piercing a child's ears may not technically be illegal but as per a PP, piercers can't get insurance now to pierce a child that young so it's clearly a very big issue that even the piercing industry recognises.
I can't even begin to comprehend why anyone thinks it would be OK to do something to their baby's body that is permanent, unless medically indicated.
But quite aside all of the ethical issues, it often causes problems for the piercing anyway as the child grows, and it can also damage the ear cartilage.
So, plenty of reasons not to pierce a baby or young child's ears that are both ethical and medical. In contrast, what's your reasoning for piercing a child's ears? "Because it looks pretty" or "because she asked for it"? Doesn't even come close to a compelling counter-argument.