There are good and bad sides to most phenomenons, smurfing just happens to have a lot more of bad ones. To the extent that most people trying to justify smurfing are in fact smurfs themselves. Don’t forget that about one user over five is a smurf after all.
I’ve always wondered if they didn’t feel somewhat bad about it. I think the truth is that what they say to others, is what they might be repeating in order to convince themselves in fact. 
It’s clearly a bother to low and intermediate levels. It can create irritation, rage, and indeed in some cases discouragement. And at higher level, hatred erroneously directed towards balance or unranked. I’ve witnessed all of those.
An interesting fact about it is that a minority of smurfs will revel and enjoy in triggering those emotions in their opponents, by making various unpleasant comment during and after the game. That, however, isn’t the case of the majority, most of them just being players having lost the will or courage to face the regular ladder’s challenge.
Hence the very title of this thread. 
Erh… not sure to follow your reasoning here ! 
You have to realize that the ones you’re gonna punish by smurfing here, are only the regular players. That’s a curious mindset to try to denounce an affliction by joining it.
That wouldn’t be the first time I’ve seen that reaction though, there has been about 3 players in this forum deciding to smurf because of smurfing. Some of them did it by discouragement, others to try to punish the devs for their inaction. I’ll repeat you what I said to them : the only ones you would be punishing by that are your brethren. 
YES, THERE ARE ! Hear me, senpai !!
https://i.postimg.cc/tJst757B/Rainbow-dash-megaphone-gif-Derpicdn.gif
Jokes aside, I’ve been listened a handful of times by the devs on balance questions. I’ve been trying to about smurfing since a few occasions, but hadn’t finished surveying the metal leagues at that point. Maybe I’ll be able to get to them in the next feedback, but we have to prepare for the eventuality of them not wishing to do anything.
We’ll agree that in that case it would eventually ruin the game ; but hey, its not like they weren’t warned. However, we players also have a couple of things we can do on our side against it. So this thread is really aimed both to the blue ones and us regular players. 
I think that’s not exactly comparable to smurfing. A smurf cheats the matchmaking, not the game itself. The race, the tools he is using is the same than the other players. It’s just like playing against a more experienced chess player, only against one that would pretend not to be. Smurfs are liars, not cheaters.
However, toxicity tends to add to itself, and I think there is a higher proportion of hackers and botters among smurfs than among regular players. And so if smurfing by itself doesn’t makes one a cheater (matchmaking put aside), most hackers I’ve confirmed were also smurfs simultaneously. And some use botting as primary smurfing mechanic. 
So it’s possible fighting smurfing might also help against other forms of toxicity.