Noch ein paar Feinheiten und Anregungen:
Approximately 500.000 Mexicans immigrate illegally into the USA every year. This is the main reason[,]for foundation of the so called ‘Proposition 187’ party : the intend to fight [against] this phenomenon[,] by aggravating the treatment of illegal immigrants. Of course there are some arguments[,] for this party and some against it.
To begin with the arguments for the party, one hast to put oneself into the Californian's shoes.
It is a fact that many of the numerous crimes in the USA are committed by immigrants.
Particularly illegal immigrants are endangered of becoming criminals because nearly all of them live in existential misery (?) and do not see an alternative way out of their misery.
Furthermore, the Americans claim that the Mexicans destroy their labour market by doing the same work as the Americans for lower wages. In truth, many Americans seem to be too arrogant to do lesser jobs, what forces the employers to lower(senken) the earnings even more. (das ist unlogisch: wenn die Amerikaner sich zu fein sind, Jobs anzunehmen, und es deshalb nicht genügend Anwärter gibt, sollten die Löhne eigentlich steigen)
Another important fact is that Americans have to pay for the deportation of every illegal immigrant through their taxes, which is quite expensive by the number of the illegals.
But now let’s talk about the arguments against the party. (etwas informell in einem solchen Text, vielleicht lieber: But of course there is another side to the coin.)
We should not forget that every person is a human being and should be treated equally. Everyone should have the same rights and nobody should be discriminated against (feststehender Ausdruck).
Although most Americans don not want Mexicans, employers use them anyway to make more money.
To come to a conclusion, every Amercican is looking for his own greatest profit (eher: benefit). On the one hand, they use Mexicans for have cheap labor, but on the other hand, they want to push them out of their country.
In my opinion, the script (?) of the Statue of Liberty " bring all persecuted persons who wants to be free to me " should be obeyed by more people because actually every person in America is an immigrant. That does not mean that Americans cannot do anything against illegal immigration, but they should treat the legal immigrants a lot better.