[Boromir88]

Unfinished Tales makes mention of the local population hating the Numenoreans because of the Numenoreans tree-felling and vast devastation of the woods in that region. And this later caused issues, by aiding Sauron and ambushing Numenoreans when they got the chance. But as Findegil said, Tharbad and Lond Daer were Numenorean settlements. I'm not aware of any reference to the Numenoreans allowing Sauron to pass Tharbad and invade Eregion. In fact it was because of Tharbad that Ciryatur was able to lead a Numenorean force up the Greyflood and route Sauron's forces from behind.