It's not about double standards. Just read his posts from the start of this topic, one by one. There is an escalation and continuous trash talk. If we wanted to judge by a single harassment, he would have earned a warning as well, as he also used the same phrase.
If you ask me, I don't like it or use it but the fact is that he is the first to call this unacceptable after he already used it in the same topic. So what I am supposed to do, start giving warnings for something that has been okay till now? This cannot happen,it is late for this. I guess we should put this to the list of harassments, from now on, right? Although, to be fair, calling someone for attention whoring does not sound the same to me by calling someone an a. So I leave for you to decide, to see the difficulty here.
So, the important step here is to realize that any harassment will inevitably create more. All sides need to zero it. Who gets banned in the way and who got a warning or not is not as important. Mack could have earned 3 warnings only in this topic today. This would have earned him 1 day ban. So what? What will this change? Even if it was a 2nd time, if would be a week. It's not a big deal either, the punishments are minimal. Many times after all, pms are sent instead of warnings.
Warnings are actually only a method to signal that it is time to stop as there is no more patience or leniency left. Most players tend to understand this and I hope Mack as well.
To close, I will remind here that Clockwork has 2 warnings. Which shows that none is above the rules and that everyone might overextend at times, including player admins. The rest should keep their cool and judge on new cases, forgiving the closed ones.