Froth and volatility are bad if they result in a less good allocation of resources in a Pareto sense. So if net utility in society decreases because some hedge funders are skimming the financial froth rather than putting resources to productive use then yeah that is bad.

For example there may be a student who is good at Math who could become a PhD physicist or material scientist and develop new materials for medical application. Instead he is drawn to wall street and spends his career optimising "high frequency trading" algorithms and pricing options. Maybe he makes more money as an individual but society as a whole is worse off from the misallocation of resources.

Basically a financial sector that rewards non-productive work exerts a negative externality on society, particularly in terms of opportunity costs and mis-allocation of human resources.