IMO, most critics of FP or OOP do so because they lack a full understanding of one or the other. Either paradigm can be applied incorrectly and cause plenty of problems. Both have their merits and strong points. Each fits a different type of project better than the other. Also different people tend to grasp or appreciate one or the other better naturally depending on how their brains are wired. More logical, abstract thinkers tend toward OOP while more right brained people tend toward FP. There is nothing wrong with this. There is also nothing wrong with learning the benefits of the "other side". If fact it is quite beneficial.

some language designers see and fully appreciate the benefits of both. They start putting class synonymous structures in FP languages or FP functionality in OOP languages. This is the future of the mainstream (Ex: EcmaScript 6 has classes/types, C# has Linq, closures, lambdas ETC).