My friend Seth Jayson, co-advisor of the Motley Fool Hidden Gems service, was chatting with me the other day at Fool global headquarters. We were talking about what is probably the most hated sector today -- health care, a sector I'm quite familiar with as the Fool's online editor for biotech and pharmaceuticals. And why is it so hated?

One word: Obamacare.

Mention that word at work or a party or a town hall meeting and you're going to be in the middle of a swirl of controversy, no matter which side of the issue you support.

A year or so ago, the most hated sector was banking, anything to do with financial services. And no wonder. Companies like AIG (NYSE:AIG) and Bank of America (NYSE:BAC) just about took down the entire world economy. And the fact that executives and employees were still raking in millions of dollars in bonuses fueled the anger.

Today, it's health care. Not for the same reasons, but for reasons enough.

And where there's emotion, there's opportunity.

Exhibit A
Insurance company CEOs like Stephen Hemsley or William McGuire before him at UnitedHealth Group (NYSE:UNH) raked in more than $12 million in compensation for five of the last six years. Ronald Williams at Aetna (NYSE:AET) has been paid more than $19 million each of the past three years. Meanwhile, the company may turn down your claim because you've reached some arbitrarily set lifetime cap or deny you or your spouse any coverage because of a pre-existing condition, without offering an alternative which helps the business recover higher expected future payouts.

Big pharmaceutical companies like Merck (NYSE:MRK) and Pfizer (NYSE:PFE) charge more for drugs here in the United States than they do in places like Canada.

Facts like the above, combined with a lot of fervent feelings, serve to make the health-care sector one of the most reviled industries today.

Exhibit B
Investments in industries hated by investors tend to perform very strongly after the hatred moves someplace else. That banking sector I mentioned earlier? Well, investors who saw through the fear and loathing have had several chances to double their money or more over the course of this year.

Another example: Remember the auto bailouts? Remember when the executives of Chrysler and Ford (NYSE:F) flew to appear before the Senate and the anger that generated? Partly as a result of the feelings felt at the time, Ford and auto parts suppliers like Autoliv and BorgWarner were driven down as much as 80% in the course of a year. However, Seth saw a good company punished too much and picked Autoliv for Hidden Gems subscribers at that time. By looking where others weren't, he helped investors who followed along to more than double their money since then.

There is no Exhibit C
I'm not saying that investing in a sector just because it's hated will lead to massive returns. What I am saying is that smart investors look carefully in those sectors for the best companies, companies that might have seen their share prices unduly punished merely through association.

Further, outsized returns don't come to investors who wait until everything turns peachy again, either in a sector or the market generally. Warren Buffett reminded us of this when he said that we pay a high price for a cheery consensus. Oftentimes, to get those home runs, we have to look in areas the market hates.

That's why Seth and co-advisor Andy Cross recently purchased inVentiv Health for the Hidden Gems real-money portfolio. As they wrote before buying shares, "InVentiv has been in Hidden Gems land for quite some time. ... The company has established itself as the quintessential one-stop-shop for Big Pharma and other companies in the health-care sector." Add in the drop in price and sector-membership, and the company appears golden.

Seth and Andy are dedicated to looking even deeper in the health-care sector. One of their latest portfolio candidates is a heavyweight which Seth believes has been left for dead by Mr. Market amid worries about the health-care debate. To show what he means, and as a bonus to members, Seth is preparing a short video in which he walks through his valuation thesis of this company.

To find out what this Gem is and why Seth believes it's worth investing in today, sign up for a free 30-day trial to Hidden Gems. There's no obligation. Simply click here.

Jim Mueller doesn't own shares in any company mentioned. BorgWarner, Laboratory Corp. of America, and UnitedHealth Group are Stock Advisor picks. Pfizer and UnitedHealth are Inside Value choices. Autoliv and inVentiv Health are Motley Fool Hidden Gems recommendations. The Fool owns shares of UnitedHealth and inVentiv Health. The Fool's disclosure policy loves controversy because it creates opportunity.