Certification either means something or it doesn’t. If being certified is a requirement for these mechanics, then uncertified aircraft mechanics (and their employers) should be prosecuted in an appropriate manner.
If certification is not a requirement, then the complaining mechanics are off base.
JMO, of course.
Certification is only good if the paperwork is real and true. Otherwise, it means nothing at all. If Jose has paperwork showing he’s a certified jet engine mechanic, but he doesn’t know how to run safety-wire in a tightening direction - how valid is that paperwork?
If the paperwork is false, then the fake mechanic and his employers should be looking at jail time.