It's not my opinion, it's my direct observations over my 40 year career in the building trades. I've witnessed everything I've spoken of, up close and personal, from growing up around my grandfather's construction business, to the last twenty years running my own.
I've got a database of twenty years of business records that show the steady decline in my earnings, and it's all due the steady erosion of retail labor prices in my industry. ALL of that erosion has been due to the easy availability of cheap illegal labor.
I would think a Freeper would know this fact is beyond dispute.
http://thefederalist.com/2016/07/14/4-things-to-know-about-whether-immigrants-hurt-american-workers/