Let's look at the evidence.
Here we see Hal Gill in his natural state: stupefied.
Gill (8 seasons): 20-77-97 with 588 PIM in 626 GP (+41)
Wideman (almost 4 seasons): 30-80-120 with 157 PIM in 239 GP (+23)
Wideman has much better offensive numbers, but that's not particularly impressive. The only Boston players who get more time on the powerplay each game are Marc Savard and Zdeno Chara. He has 2 goals and 9 assists in that time, which accounts for more than half his total points. Hal Gill, on the other hand, has actually never scored a power play goal . They're both middle of the line on the penalty kill, and both play a lot of time for their teams (Gill leads Montreal in PK time; Wides is 2nd for the Bruins).
The main thing these players have in common is their commitment to going past simple medioctriy on defense. They are often a genuine liability to their team. For example, in game 5 of the 2008 Stanley Cup Finals, Hal Gill hit fellow Penguin Ryan Malone in the face with a slapshot when Malone had already broken his nose in game 1. Malone returned, but looked like a character from Lord of the Rings.
On the topic of directly causing their teammates bodily harm, Wides broke Patrice Bergeron's thumb with a shot in MSG earlier this season. Since Paula and I had made the trip all the way down to New York to see the Bruins play, we were pretty angry about Patrice's game being cut in half. And also about the two weeks that he would spend out of the lineup, all because of Wideman.
The mistakes they both make are noticeable and therefore memorable, and over time Bruins fans learned to spot their failures a mile away. While this isn't an easy position to be in, Gill was never smart enough, and Wides may never be level-headed enough, to play their way out of that doghouse. They both seemed destined to fill the same role.
However, I don't think Wideman is the new Hal Gill.
If there's one major difference between the two, it's that Wideman can be better. Last year he was confident with the puck, jumped up effectively into the play, and rarely made horrendous defensive zone mistakes. As his year goes downhill, however, that season seems like more and more of an anomaly, rather than his "true potential". He's had only short stretches of mild confidence, and right now he's awful. Wides is running out of chances to show he can be the kind of steady defenseman that doesn't frighten our goaltenders. If he can pull it off, he has a chance at redemption. If he doesn't, which is the far more likely option, then he won't become Hal Gill. He'll be worse than Gill, because he could have been better.