Betrayal is a feeling which - reasonably or unreasonably - many Devils fans have experienced in the past couple off-seasons. Players whom many New Jersey hockey supporters had grown to admire over the years have up and left (each under vastly different circumstances) leaving those who once cheered them on behind.
Free agency in sports (or in Kovalchuk's case, random out-of-left-field "retirements") produces these types of situations frequently. Players who make a name for themselves in a given arena will move on to a new opportunity, leaving fans to reconcile their prior contributions with the fact that they are now suiting up for a different set of fans somewhere else. With Zach Parise, Ilya Kovalchuk, and, to a lesser extent, David Clarkson walking out the door for greener pastures in the last 13 months, Devils fans have seen a lot of big names vanish in a short period of time. Those departures, particularly those of Parise and Kovachuk, have produced a lot of venom within the fanbase.
How much of that vitriol is deserved? Does any player owe their fans or organization anything? I think it's a tough question to answer. Sports fandom is an irrational endeavor, but I will attempt to look at this as rationally as I can.
I guess the short answer here is "no." There's more nuance to it than that, but the bottom line is that sports is a business. It's hard for me to blame a player on a personal level for doing what is best for themselves versus an organization (not specifically the Devils, more all sports teams) who would likely dump them in a second if it yielded a net gain. If players want to use their leverage to maximize the benefits for themselves and their families, it is their right. I get a little annoyed when people start throwing around words like "honor" or "character" with regard to where a guy chooses to play hockey (looking your way, Don Cherry and Jeremy Roenick). "I wanted to go home" has quickly become a trope I loathe as a fan, but that doesn't mean it's not still a valid reason for taking a new job on a personal level. Nobody would question your moral fiber if you chose to leave Bank of America to take a higher-paying job at PNC that is closer to home.
Kovalchuk didn't cheat the Devils (to be honest, he probably did them a favor). He honored his contract until he and the team mutually agreed to no longer have a contract. Why people take personal offense on behalf of the organization is a bit of a head-scratcher to me. I have little doubt Kovalchuk played his butt off every single night while he was here. He changed his game to fit better with the team and played roughly a billion minutes a night (give or take). He won't receive another cent from the Devils, so it doesn't seem worth it to feel morally wronged on behalf of James Vanderbeek or Lou Lamoriello.
To be clear, I'm not saying there's anything wrong with being upset or mad about a departure as a fan. I'm plenty mad at Ilya Kovalchuk and this whole situation (even though it's probably much better off long term) and plan to boo him unyieldingly if he ever returns to the NHL in another uniform. Fans invest some level of financial and emotional capital in a player when they are part of their favorite team, so them bailing means you lost out on your investment to a point. Boo away, readjust your sports fan biases, and hope for his failure in all of his future on-ice endeavors (I know I will). Just don't tell me Kovalchuk - or Parise or Clarkson, for that matter - is a bad person because he followed the money, or his family, or his home.