I just had a look at ancient trenches as well. You have to give the author credit for imagination. While, yes we read this and quickly see it as entirely unsustainable, it is a pretty fun read. I know I'll get flak for saying this, but I actually really enjoy talking with people who have ideas like this. I don't know, I think there is a value in interpretations of the naive and uninformed. Kevin Woolridge has rightly pointed out that this person has clearly never had much constructive criticism. If they had, I think they definitely could have gone on to do alright in university because there is definitely potential for creative opinion if they were better read.
But really, connecting megaliths to archer towers makes for pretty cool imagery when you imagine such a battle playing out in your head...and it isn't impossible to imagine some megaliths somewhere being part of a battle landscape backdrop of a later, say, medieval battle, etc. Very un-archaeological, I know, but there is no harm in constructing fictional narratives around archaeological/historical evidence. Maybe this person could go on to found a new literary genre of "archaeological fiction." I guess my point here is that I think its alright for people to explore alternative narrative avenues to bring these things to life. Its a fun pastime - though I wouldnt advise submitting it at conference :o) of course with better information these narratives play out better in your mind. Come on, you know you all do it when you are on a site.
But in all seriousness, he is right to consider the possibilities when he says: "I believe their purposes were utilitarian and served a myriad of functions including but not limited to navigational devices, borders, and defense lines for the ancient mining and trade industry" but loses it at "in an era of archery warfare." In this person's inexperience with prior scholarship they naively do what any good academic should do, be critical of the evidence and try to punch holes in the norm. With better information, this person would have better questions. I wouldn't write this person off, they'd probably be fun to chat with at the pub.
But of course, there are those who might take their pseudo-archaeological narratives it a bit too seriously...the pyramids of Eastern Europe come to mind (I wonder whatever happened to THAT guy)