An ESFJ being diplomatic is very Fe (our primary function). It's because an ESFJ wants to speak the truth, but also wants to keep others happy and harmonious so being diplomatic can be the best of both worlds for us. I admit, I often do this and I think I'm being clear.
I still don't see why MBTI would say you would never work. I think anyone can work as long as there is a lot of understanding and acceptance (not to mention selflessness). One website said that a perfect match for ESFJ would be INFP or ISFP - which personally I don't really see how that would work for me. I love INFPs, but their egalitarianism tends to drive me crazy and they are too "easygoing" for me. ISFPs are a bit of a mystery to me also... but I'm trying to learn to understand them. :-) But that's me. I want to understand EVERYONE! And make everyone happy. Lol