Our good friend Jim Cramer went on a rant last night on Mad Money about the shortcomings on the United States Oil Fund (NYSE Arca: USO).

According to the digest at TheStreet.com: "Cramer took aim at the United States Oil ETF in particular, calling the fund simply a travesty.

Cramer said the United States Oil Fund is not what it promises. The fund does not track the price of crude as it claims. Since the fund's [inception], crude oil has fallen 23%, yet the fund is down almost twice that at 54%. Just this year, oil is up 18%, but the United States Oil Fund is down 6%. This fund has nothing to do with oil at all, he said.

Cramer said the problem with the fund is that it doesn't buy oil, and instead buys oil futures. Since oil futures expire, the fund rolls over its contracts every month, incurring costs and expenses it'll never recover. Cramer said while the operations of the fund are legal, and listed in the [prospectus], investors need to steer clear at all costs."

As anyone who reads this blog knows, for better or worse, I've been writing extensively about the differences between USO, its sister fund USL and spot crude oil. As a general rule, I like that Cramer is at least talking about the fact that USO will not perfectly track the spot price of crude. That's an important message to get across.

The problem—as it always is with Cramer—is that the nuance is lost. USO is not a terrible investment. It is not a "travesty." It does what it says it does, which is invest in crude oil futures. By Cramer's argument, you would not want to invest in any commodity futures ETF ... ever ... because they don't track the spot price of commodities. That's crazy, considering the wealth of academic evidence supporting the use of commodities in asset allocation strategies.

The real problem with USO and other commodity ETFs is simply that many investors are not used to operating in the commodities market. We grew up on stocks and bonds. Now, the ETF market has opened up new markets like commodities and currencies to everyday investors for the first time ever, and we don't fully appreciate how they work.

As a result, people are surprised when USO doesn't track spot crude perfectly. They don't understand the influence of contango, backwardation and collateral return; they don't understand the tax treatment of commodity futures.

That speaks to the educational burden. It means people like me aren't doing enough to educate folks about the way these funds work. Because while it is a little complicated, it's not impossible. The information is at your fingertips. You can find out the level of contango in the oil market, for instance, by looking at the prices here. It just takes at least a little bit of work.

I did have one final thought for Cramer: Who really wants to own spot oil anyway? The spot price of oil has risen at a 2.5% annualized rate for the past 30 years. Over that stretch, futures have been a better bet by far.