If you make 250k a year, you pay a lot in social charges, but not as much in percentage (usually retirement charges are regressive) and in exchange you get unemployment checks and retirement that are proportional to how much you've put in. In short you get back what you've put in.
On the other hand income taxes are usually progressive (the richer you are the larger the percentage you pay) and richer people benefit less from them, in that they go to finance public transportation, education and hospital which rich people tend to use as much if not less than commoners.
Nobody making moderate capital gains would pay these charges voluntarily, in exchange for benefits it gives them. Thus it makes complete sense to lump it in with the other capital gains taxes when discussing incentives.
From Wikipedia:
"The mandatory state pension is an unfunded contributory penison based on redistribution of contributions from those working to those in retirement. The scheme aims to provide up to a maximum of 50% of the retirees highest earning years up to a limit of 35,000€ annually (in 2010)."
Almost nobody who pays taxes would pay them voluntarily, especially the rich who get no benefits from paying them. Yet we force them to, it's the redistributive nature of taxes.
In the case of significant capital gains, the taxpayer is unlikely to be a welfare recipient, and is paying into the system without benefit.
I have no problem with this; it's the nature of taxation. But lumping it in with general taxation is not misleading at all.
If it were a superannuation scheme, and you got the money back when you retired, you might have a point - but it's not.