I agree with the sentiments of your comment, however:
"tax never killed anyone"
The Loan Charge is a tax and has caused 7 suicides so far.
While I believe the loan schemes were highly unethical, and I advised my father to avoid them like the plague*, they were "sold" by experienced tax advisors and legal experts on the basis that they were legal. While strictly, the way the regs are worded, the loan charge does not count as retrospective taxation, the effect is to raise extra tax on cases which should be settled. This is at least as unethical as the schemes themselves.
The stupid thing is that there were already ways to deal with this in the tax code, by means of investigations and anti-avoidance rules. The loan charge is just a way for HMRC to avoid doing any work, avoid scrutiny for their failures in investigating this in the past, and to open up years which should have been closed already.
* I wasn't contracting at the time but he was and nearly joined such a scheme. He's very glad he listened to me now...