It has been tagged since 04:15, May 21, 2015 (UTC).
The specific reasons are: see talk page.
One of the help files distributed by the DHS included (in UUcode form) a simple icon based on the Doom logo (it was a standard 32x32 icon in the 16 fixed Windows colours, that being the only format supported by most Windows implementations at the time). Another British Doomer (who wishes to remain anonymous for reasons which will become apparent) extracted this, recoloured it with a transparent background instead of a white one, and also produced versions for Doom II, Doom WADfiles (logo superimposed on maze), Doom save game files (logo on black 3½" floppy) and Doom demo files (logo on red 3½" floppy). He bundled them into a single DOOM.DLL file and emailed this to Mapleson with a description of what the file was.
Unfortunately, athough Mapleson duly set up a "download" page for this file, for some unfathomable reason he included the raw UUcode for the file instead of a download link to the file proper; it is reported that many people missed out on the icons because they couldn't understand what they were seeing and thus didn't realise that all those strange characters could be fed into a UUdecoder and out would pop the DLL file. Even worse, the page was worded in such a way as to imply that the DLL's author was the author of the page itself, rather than just the contents, and was thus responsible for it. This resulted in plenty of flame emails (the author's email address was disclosed), the first few of which were baffling as they not only assumed that the DLL author was also the page author, they also made the further two false assumptions that this was his only page (when in fact it wasn't one of his pages at all) and that he thus would automatically know what they were talking about without their needing to bother with giving the URL (in fact the DLL author didn't even know the page existed, much less what the URL was, as Mapleson hadn't informed him). As far as is known, Mapleson never corrected this mistake by putting up a proper download page.
The DLL author rectified the situation by putting up a download page of his own, but this mainly resulted in further flames from people who reckoned that they could "do better" despite the severe limitations already mentioned; these even included death threats from one particularly nasty individual (over a set of Windows icons?!?! If he disliked them so much, nobody was forcing him to use them). Not surprisingly, none of these people ever (as far as is known) put their icon editor where their mouth was, to prove this claim.
To the best of anyone's knowledge, the icons are now lost due to the trolls.