Should have been

"That there should have been a propagandistic motive for much of what Stalin said should not be surprising."
"That there should be a propagandistic motive for much of what Stalin said should not be surprising."

Should I use "should have been" or "should be" here? What I am trying to do is to suggest that much of what Stalin said was propaganda and that this should surprise no one. I want to put this forward, however, without adducing any actual evidence to substantiate it.

Thanks.