As easy as learning a dysfunctional one if not easier.
Now scheme may not be the best example of this as its syntax is entirely alien (then again all syntax is, when you've never developed), but the canonical is the following statement:
x = x + 1
If you've never developed before, the only place where you've seen something like this is maths, and in maths this is completely nonsensical.So learning imperative programming does require lots of deprogramming and reprogramming of your brain. Which make up most of the hurdles of learning an FP (or logic, or dataflow, ...) language later on: your brain (or its section that has to do with development) has been baked in imperative idioms and methods, FP languages not only don't use these but use completely different techniques to solve the same problems, so you have to "unlearn" the old ones and "relearn" the new ones.
Now, I'm sympathetic to your final paragraph, but having never taught functional programming to anyone, I can't corroborate it. Personally, I went through something similar when first learning how to think functionally.
It is akin to writing a text in your favourite text editor versus writing a text in Word. The latter will distract you with mark-up, random auto-'correction' and other diversions I'm still repressing.
The best thing one can do is get The Little Schemer[1], download DrRacket[2] and go through the book.
[1] http://mitpress.mit.edu/catalog/item/default.asp?ttype=2&...
In the second half of the course, where you learnt Java and OO, was totally confusing to most those who'd just learnt Haskell as their first language and many people who got great grades on the Haskell part failed the Java part.
So it would seem that whatever you learn first is easy and normal and whatever you learn after that is confusing and difficult.
The difficulty could be due to the brain damage C++ causes. Before I get incinerated, I have to remind you of Dijkstra quote about BASIC ("mutilates the mind beyond recovery").
Both BASIC and C++ (and Java, Smalltalk and so on) fixate several ideas about computing that make it harder to understand very different concepts. In a sense, that qualifies as mild brain damage.
I learned programming with BASIC on an Apple II+, went through FORTH (GraFORTH), C, Pascal, APL (The write-only language) and FORTRAN (in college) and later learned OOP with Smalltalk (and worked a bit with Actor). Did a lot of VB too (I had bills to pay), Perl, Java and Python. For obvious reasons, I don't completely agree with Dijkstra on the BASIC thing. I never liked C++ much, possibly because I learned OOP with Smalltalk and C++'s OOP seemed to me a misappropriation of the acronym. All things considered (it took me 8 years and a job offer to decide to learn C++) Smalltalk damaged me beyond recovery.
But a couple months ago I decided to give it another go with Scheme and I have been pleasantly surprised by how much more natural it seems to me. I'm having fun!