It's not your problem where the bitcoins came from if you buy them at an exchange, a regulated exchange...
If you buy them from some stranger on a back alley for hard cash, well, how will someone know those bitcoins are yours now, and if you do this you probably know the risks, and this transaction might be illegal if it is above some particular amount.
For the second part the analogy is with gold, gold is heavily regulated and no government can control the amount of gold in circulation, or its inflation.
Again, not rocket science.
Look I don't mean to be offensive according to your post count you have spent some time around bitcoin, but you don't see the bigger picture here. What you saying is true - partly.
1. It is not your problem if you buy them at exchange. It's the exchange's problem that they bought them at the first place. That means an exchange did not do the background check, which it cannot do. It is therefore again subject to a reasonable doubt that it was laundering money. If such exchange falls, because of that the price of bitcoin will go down and it will influence you because you are losing money. If this become a habit there wont be much exchanges and it will be hard to obtain bitcoins or to sell them. So it is actually your problem, if you own some BTC and you care whether it has any value.
2. Hard cash purchase - you are completely right. You laundered money, it's illegal you might be prosecuted if found and it is something every government will try to stop, but most probably fail.
3. Gold is not so heavily regulated as fiat currencies, because it work differently. Also to obtain gold you will be identified the other party will have a recipe that you bought it and again it is impossible or illegal to buy for example a $1.000.000,00 worth of gold in cash therefore anonymously. Try selling a 1000 oz of gold without proving where you got them. Its not about the amount in circulation or its inflation but about the title of ownership tied to a person or a company. The bitcoin is build on the ownership being transparent but anonymous.
4. You are right it is not a rocket science its law.