It’s easy to root for the Celtics when they are going up against the NBA’s version of Darth Vader, IRS auditors and fumbling dental surgeons. Pretty much everyone hates the Miami Heat outside of the 305 area code. In addition to playing the underdog role to perfection in the Eastern Conference finals, the Celtics have emerged as something else, something they’re not quite accustomed to being: the lovable overachiever. When ESPN had one of its instant polls after Game 2 and the question concerned the officiating, the Celtics were deemed to be the victims of bad calls by virtually the entire nation — save for the state of Florida. They haven’t lost since then and can clinch a spot in the NBA Finals with a victory Thursday night. Part of it, again, is who they are playing. Heat czar Pat Riley did nothing untoward in putting his team together, at least not in any devious or underhanded way. (You can argue he might have added another big man or a better point guard.) LeBron James and Chris Bosh agreed to take less money to play alongside Dwyane Wade, something you don’t always see in this day and age. That should count for something. It doesn’t. People hate the Heat. It may be because of “The Decision,” that dreadful, overhyped announcement by James that he was taking his talents to South Beach. Then came the utterly ridiculous dog-and-pony show in Miami, with the three of them primping like they were auditioning for Project Runway — and James predicting multiple championships. James himself has become one of the most scrutinized, polarizing athletes of our time. He’s not a bad guy; au contraire, he’s just the opposite. How bad can a guy be if he’s reading the third book in “The Hunger Games” trilogy? (I wonder if he’s a Peeta guy or a Gale guy?) But until he gets that first title, people are going to question him, much the same way they questioned Michael Jordan, who needed seven seasons before he got his first ring. As Shane Battier noted last weekend of James, “He sneezes and it’s a trending topic on Twitter. He is a fascinating study because he’s really the first and most seminal sports figure in the information age where everything he does is reported and dissected and second-guessed many times over, and he handles everything with an amazing grace and patience that I don’t know if other superstars from other areas would have been able to handle.” Nonetheless, much of the basketball world rejoiced when the Dallas Mavericks, a group of wily veterans, dispatched the favored Heat in the NBA Finals last season. Much of the nation is similarly attached to the wily, banged-up Celtics, who are one victory away from doing the same thing, albeit in the conference finals. It’s probably clichéd to say the Celtics have become America’s Team, but they are hard not to like. This isn’t a team that oozed confidence — some might say arrogance — like the title teams of the 1980s. That behavior was justifiable in their minds because of their successes: three championships and four straight trips to the NBA Finals. This team doesn’t project a similar attitude. It does have its trash talkers, no question. Kevin Garnett is the undisputed king in that department. Rajon Rondo took a shot at the Heat during Game 4 and then wouldn’t back off the comments when questioned about it afterward. Magic Johnson liked that. It’s something that the great fictional television newsman Lou Grant would call “spunk” (although he didn’t like spunk). Pierce has the reputation for being a drama queen, largely due to his knee injury/rapid recovery in Game 1 of the 2008 NBA Finals. A couple years later, Quentin Richardson called Pierce and Garnett “actresses.” But this year, it’s different. Fans have embraced this team. Part of it undoubtedly is because of the adversity it has faced, losing two players to heart conditions, a third to season-ending shoulder surgery and a fourth to season-ending wrist surgery. It never made excuses. Celtics fans have seen Garnett rejuvenated since the All-Star break. Pierce labors along with some kind of knee injury, yet manages to at least stay with James on defense most of the time while knocking down a killer three in the King’s kisser in Game 5. Rondo is a nightly tour de force. The coach is more than likeable. It’s a team stocked with “good” guys. The high-maintenance types of the past — Big Baby Davis, Nate Robinson, Delonte West, Von Wafer — all were let go. In their place came less-heralded grown-ups like Brandon Bass and Keyon Dooling. The latter is called “Reverend Dooling” for his preachy qualities and has had a huge impact on Rondo. “This is probably the most positive group of guys we’ve had here in 10 years. They’re tight. They care about each other,” said Celtics co-owner Steve Pagliuca. As long as they’re playing the Heat, most basketball fans will root for them. But if the Celtics do manage to make it to the NBA Finals, it would not only be the most unlikely such berth in the franchise’s long history, but it would also pit them against a team that is equally appealing to the casual viewer. But in the here and now, there’s no argument. They are “America’s Team” not only for what they have done and how they have done it, but also because they are doing it to the Snidely Whiplashes of the NBA. You gotta like that.