JetBrains is making a business decision. That's what businesses do. Their current Community Edition is open-source. Anyone is free to pick up where they left off. That is an enormous contribution they've already made to the community. You make your consumer decision. They make their business decision. This is the implicit but very real relationship any customer of theirs has chosen to be in.
I personally don't agree with their decision. But, I'm not running their business or working their jobs. Before going all "They're Google Reader'ing Us.", just ask yourself, do you use Gmail? Are you willing to continue their work on the Community Edition?
edit: to clarify my examples.
The services I referenced where chosen as examples of alternatives to options such as hosting one's own email or using existing perpetually or open-sourced licensed products (Gmail), a company that drastically revised it's product offering (NetFlix), and a company who's founder destroyed the business model of purchasing a c.d. for life by making mp3's user friendly and then went legit by moving to a SaaS model (Spotify).
As others have pointed out, one can still purchase a perpetual license through November, so JetBrains is not only not stealing back the product they sold you, they are also giving you time whether you'd like to make this transition with them. If not, simply do not purchase their product in the future. To expect JetBrains to do otherwise (maintain their business model) is to tell them how to make very basic decisions about how they run their business and live their lives. That, I think, is bad.
tl;dr: They didn't steal anything. Don't tell people how to live their lives.