The ACLU page is rather manipulative in that they construe the facts very favorably to the convicted. E.g. "After serving two years in prison during his mid-twenties for inadvertently killing someone during a bar fight." Oh yes, he just accidentally killed someone in a bar fight. Happens all the time really, right up there with leaving your credit card with the hostess after getting a little too tipsy.
It would be less biased to show statistics for the kind of people sentenced under the three strikes law, but that wouldn't tug the heart strings as much. California's law is particularly dysfunctional, because it applies to any three felonies while most states limit their laws to serious felonies. As a result, about half of three strikers in California are in for non-serious or non-violent predicate felonies (burglary, robbery, and drug possession). But in other states the law is more limited. For example, the Georgia law only applies to: (1) Murder or felony murder,
(2) Armed robbery,
(3) Kidnapping,
(4) Rape,
(5) Aggravated child molestation,
(6) Aggravated sodomy, or
(7) Aggravated sexual battery.
Besides that, what you're missing is that nobody is really intending for these specific, cherry-picked, people to be kept in jail for their whole lives. Their sentences are the unintended consequences of three-strikes laws that offer no discretion to sentencing judges.
When legislators voted for these three strikes laws, with public support, they were thinking of people who are "irredeemable." Hardened convicts who end up in jail on three occasions. What they didn't count on was the fact that there are people living on the edge who rack up a number of felony convictions for relatively minor things even though they're not the kind of hardened criminal legislators were thinking about. If you live in the ghetto and have friends who engage in gang activity, it's pretty easy to get drawn into some bad behavior that results in a couple of felony convictions, so that "one mistake" later in your life can bring you under the three strikes law.
Why don't these laws get repealed? Because Americans are really not sympathetic to people living on the edge. Ordinary people don't live in the kind of circumstances where they might wander into a felony conviction from a minor lapse in judgment. They don't have drug dealer boyfriends or friends who try to recruit them into burglarizing a house. It helps that 75% of people sentenced under California's three strikes law are black or hispanic (45% are black despite only 6.5% of the state population being black). Americans are particularly unsympathetic to racial minorities living on the edge.
I think sentences in the U.S. are deeply dysfunctional, but I hate this sort of publication by the ACLU. It makes people who support sentence reform seem dishonest by cherry-picking the edge cases, instead of trying to paint an accurate picture with statistics.