But if the EU just wants to punish the UK for Brexit

It's not a punishment to get a normal treatment instead of preferential treatment. If we go out of our ways to let you in at any costs, as suggested in the article, we're making all 26 current EU countries inclined to do the same shit whenever they get similar populists in charge. That will eventually tear the EU apart. Coming and going, and then getting a goddamn prize in the form of preferential treatment for having done that, is not something we should allow. Leaving should really mean leaving for good. Okay, if things change, welcome back, but why should we go with a very bad deal we were forced to accept in the 1970's when we were much weaker and had no other option? Now we can survive without the UK just fine, so we shouldn't just bow ourself into a knot in front of them like we did half a century ago. Welcome back, of course, but only with the usual rules that apply to everyone else as well.

And, I must say, I keep seeing British people see being treated normally as a punishment. That's some heavy level of exceptionalism. I keep seeing that attitude, and it's not an attitude I want to see in a EU member state. English people who are saying shit like "EU just wants to punish the UK for Brexit" when what is being talked about is just not giving them weird exemptions or other kinds of preferential treatment that puts them over other countries, do a good job shifting my thinking from "you're welcome to join" towards "rather not."