Yes, you are right, because I do disagree with a lot of it. Explaining my position on that would take way too much time, but to me, just saying "it's the standard" is not meaningful. In what area of our lives do we decide to do things the way we did them 100 years ago, just because? I'm sure there are some things that aren't coming to me, but especially our understanding of animal behavior and our standards of what's humane (to all creatures, including ourselves) has changed SO much over the last century, why cling to it here?
Again, whether PETA says this or that is irrelevant. You can disagree with 99% of what PETA says, and agree with 1% of it. BTW, I have read a fair amount on PETA. Don't worry, I'm not a member.
Also, just because a dog can function without a body part doesn't mean it's not necessary. A three legged dog can run just fine, but it doesn't mean three is as as good as four.