First to explain its structure, it first says that his initial answer to the unmarried person who found himself unable to control his urges was that he was "forced" and that the situation is one where he may die if he doesn't do it (!) and thus not liable. I'm leaving that aside because the principle is true, the application is off but that is less black and white. Either way one is not "forced" if he just says I'm allowed to do it, so there is little point in dwelling on that. And there is no tradition that failure to have marital relations is potentially deadly, nor do doctors agree. As far as I can tell he just makes that up claiming it is comparable to other cases.
He attributes the position that it isn't an issue for an unmarried person to waste seed to the העזר מקדוש which is a commentary to shulchan aruch by the same author as the אשל אברהם (as this author himself writes). He derives this from the idea that the העזר מקודש holds the prohibition is rabbinic and the permission for interactions with one's wife that may lead to wasted seed. Given how off this Teshuva is I'm not spending the time to verify that this claim is correct (this is a known opinion that is usually attributed to the Drisha and not regarded as the Halacha - you can see Bnei Banim among other places that mention it - I'm just not going to see if the העזר מקודש contradicts it elsewhere and thus can't be said to agree with it), but his derivation is certainly not correct.
The אשל אברהם (the same person) to S.A. O.C. 3:14 s.q. 1 says on what the S.A. says that an unmarried person may not touch the Glans when urinating because of the concern of wasting seed, there he specifically speaks to the fact that an unmarried person is stricter than a married one and is strict in the prohibition of rubbing or holding for a married person, in the notion of "even a married person" where a married person might have reasons to be lenient. He doesn't come along and argue that there is no problem here because there is no prohibition or anything like that. This is the quote of the אשל אברהם:
נשוי ובסעיף י״ז[ט"ז] ז״ל לא הותר לנשוי לאחוז באמה אלא להשתין אבל
להתחכך לא מעתה אין הכרע אי מותר לנשוי להתחכך למטה מעטרה או לוקא
להשתין מותר ועיין ב״י מ״ש בשם סמ״ג שהביא ספיקא של מהרי״ל ז״ל בזה
לענין אחיזה באמה ע״ש ובת׳ שב יעקב סי׳ ל׳ האריך למעניתו ופסק לאף
לנשוי לא שרי להתחכך ט אם מעטרה ולמטה ע״י כתונת לוקא ולפניו אפי׳
The rest of this is of similar quality, including the tenuous claim that marital relationship with a woman past child bearing years is the equivalent of wasting seed (see here). He doesn't even consider a different possibility and rejects it. He asserts these derivations as "obvious".
If someone wanted to spend more time on this I'm sure it could be more thoroughly refuted, but I think this gets the point across.