I 'love' the broad statements that folks make and assume that they are true.
Yes, going to a third or fourth tier school in today's economy is a bad idea for most people. Heck even going to a T2 school is a bad idea for most people. However,there are EXCEPTIONS"
First, if you are in or going into a field where a law degree is considered very useful, going to a lower tiered school might be fine as long as you have no ambitions to get a job with the bigger firms. A good example would be a hospital administrator who wants to go to law school part time, which should probably be benefical to their job. A financial planner who goes to school part time, would also benefit from law school training as would a current IRS agent.
Second, if you have a guaranteed job connection, such as working in dad's law or accounting firm, going to any law school would be fine.
Third: If you had parents that have more money than sense, and you REALLY have a realistic plan as to what you want to do with your law school training, going to a lower tiered law school might made sense.
Fourth, if you get a completely free ride that doesn't require high levels of attainment in order to keep the scholarship, going to a lower tiered school might be fine.
Fifth: If the lower tiered school is the best in the state and you want to practice in that state, going there might not be that bad.
In almost any other circumstances, I wouldn't recommend going to a law school in today's economy that is T2-T4 ranked. Heck, I wouldn't even recommend T1 schools unless they are ranked in the top 20. Even with this, I don't think I would recommend taking on a lot of debt.