Looking for s2, I'm not going to get in to a debate  with you over this.  From past experience I've found your arguments  interminable.    It's like arguing with a birther over Obama's citizenship.  

To be clear, the burden of proof is on you to show that this dramatic Constitutional Act did not diminish African-American immigration to Oregon.  I hardly have space here to list all the obvious evidence, such as the higher black population in California and  Washington, but you can find them in any good Oregon history book.  I urge you to go find and read them.  

Frankly I'd never heard a serious argument AGAINST this view of  the  Exclusion  law until recently when some of Deady's powerful legal friends  rushed in to Pooh Pooh its demographic effects.
Your ideas, that blacks were too ignorant and ill informed to know that "Oregon did not welcome Negroes", and "there was nothing here for them" are remarkably  ill-informed.  
Please don't demand evidence from me again, just go read.