>The purpose of the bulk surveillance is absolutely NOT to gather evidence against citizens.
They admit themselves they gather bulk data on everything. The intent of an organization that has proven to lie through their teeth and break the law really means nothing. Intent is also pointless, the action is what matters.
>In fact, it is used agains foreigners only for national security and intelligence purposes.
This is simply not true.
http://www.theguardian.com/world/2013/sep/27/nsa-employee-sp...
www.huffingtonpost.com/2013/11/26/nsa-porn-muslims_n_4346128.htm
www.slate.com/blogs/future_tense/2013/08/23/bloomberg_report_nsa_employees_have_deliberately_abused_their_power.html
http://www.businessinsider.com/how-nsa-can-abuse-data-on-ame...
https://www.rt.com/usa/nsa-domestic-surveillance-abuse-684/
There are hundreds of resources and examples showing rampant abuse and non-security related surveillance of Americans.
edit: don't forget its use for corporate espionage: http://sputniknews.com/latam/20150707/1024322295.html