A bit of a stretch to call a lethal injection violence imo, but in any case it's many levels below the violence a killer deploys on their victims.
As for animal practitioners, there is a whole infrastructure of dog training, people are used to teaching them, etc. While training pigeons to do tasks is a specialty field probably at a limited level for lab research. Could be scaled up. And one advantage is the pigeons could do their radiology reads in a research lab, so they don't need to interact with patients, as dogs need to to sniff out cancer.
I spotted an article last week that headlined dogs sniffing out CV infections form armpits, but I didn't click through. I assumed if it is viable we'll be hearing more about it soon enough.