Antonio, why would you tax government benefits? Seems a bit redundant, no?
This provides a corrective to the situation where, by the very design of a program, people end up getting too huge checks from the government. For example, in most countries, unemployment benefits and pensions are based on previously-earned income, which means that wealthy people get comparatively more (and, since the income is pooled in the household, the problem gets even worse as one of the spouse keeps earning a high salary alongside said government benefits). Changing this system would be impractical both politically and economically, but at least we can still make sure that those who get the juiciest deals pay their fair share back to the State.
That's understandable, but IMO, it would make more sense to stop basing benefits off of previously earned income in the first place.