You would be unable to cite sources for the"illegality" of the settlements, as there are none. The settlements are built on disputed lands no doubt, but lands that no "Palestinian" country or sovereign political entity has ever had title to. 

Israel has every right to construct settlements on "disputed" lands, until such time as title can be proved to be held by another sovereign entity. The court of public opinion, led by 180 countries that have routinely demonstrated an overwhelming anti-Israel bias, has no standing in this matter, except to those that share that bias.