Since the student is obviously in agreement with the remainder of his lesson, we shall address that portion which has brought cause for contention. To wit, that 'the labor theory of value is simple'.
In the 19th century, there was cause for quantifying everything in simple, easy to understand terms. There was, also, an equivalent intent in the medieval period in regards to astronomy. In the quest for cosmological understanding, it was contended that the earth was, conveniently, at the center of the universe. Revolving, if such a phenomenon existed, was done in reference to this body. As a theory, it was elegant and simple - any celestial object might be tracked easily enough in reference to this body, and nothing as difficult or as confusing as ‘Newtonian physics’ had been proposed as of yet to refute it. Now, it is true that subsequent measurements and models based on said came to be wildly flawed, leading to all sorts of complicated and farfetched excuses for the discrepancies found, but the main theory - the earth as the center of the universe - was easy enough to accept.
Imagine the introduction of massed objects as various local ‘centers’ … Utter confusion! If objects revolved about any old massed object sufficiently large, what meaning then did the term ‘center of the universe’ hold? What of all that brilliant effort spent on apologizing for what had obviously proved to be a blatantly incorrect thesis? Best to burn the supporting documentation (and those who had generated this affront to the intellectual status-quo, for good measure).
We are at a similar impasse in regards to Marxism. This simple premise, that labor - not desire, or usefulness - is the basis for the remainder of his analysis. In and of itself, it is easy to understand, and if one is not particularly worried about being right, an idea that can be readily absorbed by anyone. Admittedly, because it is wrong, it does lead to all sorts of confusing and spurious diatribes into the dominions of the ridiculous and the fantastic (and, all to frequently, into the realm of tragedy). It is also true that these jaunts tend to be the engine for inspiring a great deal of "gordian" prose (a talent for which the comedy team of Marx and Engels most certainly excelled), but it is hardly true to subsequently claim that the underlying theory itself cannot be readily fathomed.
Indeed, any sort of person could come up with it. Even an unemployed ne’er-do-well. Being taken in by it, of course, is another matter entirely.
P.S. We are most pleased that you have acknowledged our ordinal position. It is our desire that those below might rise to our heights, rather than the alternate proposal of a ‘leavening’ that brings all to the same, subsistent level. Feel free to trickle down to the position at which you feel comfortable at, of course - we are, after all, committed to a freedom of religion as well.