You can think what you want about derivatives with which investors can speculate on credit. In case of success, one may begrudge them this one. And you may pour malice on them if the speculation goes wrong and they lose a lot of money. As a politician, one may think that such speculation is anti-social or harmful (although this has yet to be proven).
But whatever one may think, all citizens who try to increase their money by trading securities by legal means deserve fair treatment. This does not include letting them run into the open knife. The lawmakers are also aware that it is a fine art to be familiar with the opaque German tax jungle.
There would certainly have been other options than the current taxation of futures transactions, which would not lead to the tax authorities collecting massively from the substance of investors – and beyond. Bans, restrictions, even higher or additional taxes on profits from futures transactions than on other income – all this would have prevented some investors from now facing ruin.
Wasn't the legislator aware of this? Or was it intentional? In both cases, a "yes" vote would be a shameful answer. Ignorance may not protect against punishment before the law. But it should at least prevent legislators from legislating.