> But so far no one has seen a disadvantage either. Right?
No, researchers have found disadvantages to bilingualism. Bilinguals tend to know fewer words in their first language than monolinguals [1]. Bilinguals also experience more tip-of-the-tongue moments [2,3] and are slower in picture-naming tasks than monolinguals [2].
> What other group would you prefer to have a monopoly on violence?
The people. Governments can be illegitimate, e.g. not derive from the consent of the people, in which case government monopoly on violence yields oppression.
Violent revolutions are sometimes necessary in the course of human events. Without the people having the capacity to wage war on their government -- that is, the capacity for violence via the right to bear arms -- such revolutions are not possible.
No, researchers have found disadvantages to bilingualism. Bilinguals tend to know fewer words in their first language than monolinguals [1]. Bilinguals also experience more tip-of-the-tongue moments [2,3] and are slower in picture-naming tasks than monolinguals [2].
[1] https://www.psychologytoday.com/blog/life-bilingual/201306/d...
[2] https://en.wikipedia.org/wiki/Tip_of_the_tongue#Effects_of_b...
[3] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2862226/