Aliens: Debate

I think Terrance Mckenna brought up a good point when he said for us to think aliens are going to come in metal ships and want to trade or take over earth is called Failure Of Scale. He said whatever is out there we have to assume is completely beyond out imagination. They grew on a different planet on a different side of the universe under different chemical makeups and laws. Etc. now i do believe there is life out there and there is alot of compelling evidence but to assume they are humanoid and somewhat like us is definitely failure of scale.