why keep interest low over long term is bad policy

Fed is trying to keep interest rate at zero for long term. The question is not how low the rate, it is the duration. If interest rate is kept low for extended time, people's behaviour change. The long term consequences are
1. encouraging consumption and discouraging saving.
2. encouraging borrowing, especially government borrowing which will be addictive
3. encouraging riskier investment which will producing bubble after bubble.

All these will make people feel good in short term but damaging in long term.