Laws which claim truth as illegal are illegal themselves.
It can be excused to forbid saying something, but to force lieing not to an enemy - is against basic humanism. As misleading leads to harm and such that would be to force making harm to other one.

Laws are made to protect _interests_ of some people. Laws which protect interests of minorities by the cost of interests of majority are antihumanistic. Those often can be thought as illegal - as contradicting to more basic laws and interests.

There were, are and will be minorities which try to set own interests above majorities. Some of them are at power and push laws which are against majorities. They act by a lie and a force to establish such situations. It's common to have a competing between groups of people and between individs.

About to be nice.
Not all what is useful and for better - is pleasant. Examples of what are medicine and training. The reasonable is to act so, that the use was more than a harm (including emotions). The question is what is the balance - what is the use and harm to compare.
The best evaluation would be emotional - the perception of happiness degree. But this should be evaluated strategically, anyway. Where moment loses in emotions mean lesser than emotions on longer time.