It's a common problem among external facing engineers. A source of great stress also. I think it is critical for engineers to discuss this topic and re-shape our view of working with the external world. We don't operate on an island and we cannot keep going for long with a condescending view of the business types without developing issues. Figuring out a mutually beneficial / acceptable operating procedure is key. The default is too negative and helps no one. With some skill, we can leverage our position, really solve big problems, and have a better working relationship. Just my 2 cents coming from b2b where my projects have 100% external impact (i.e. if we fuck up, they will have egg all over their faces - brings out the control freak in the business types).