The problem with forums is that it is really easy for someone's intentions and meaning to be misinterpreted. Pretty soon you can end up with a ****-storm like this seems to have turned into. For what it's worth I think Mike (from Mayhems) has done the right thing and not replied - once this sort of thing kicks off, there just isn't anything you can say that will fix it.
Mike does own (as far as I'm aware) the Mayhems company. This is what he meant when he said he was "no rep" - he does represent the company but he's also the owner.
As far as "unprofessional" goes I think that, like the rest of us, Mike is entitled to an opinion and, given his potential for bias, you are free to take or leave it as you see fit. Unprofessional would have been if Mike had said that all Corsair/Antec/Asetek/Other (delete as appropriate) brand AIOs are rubbish - something he did not say. Mike is known to be fairly blunt in what he says and I think that does catch people out if they aren't used to his posts. However, his experience, knowledge and willingness to help are something that I appreciate - you don't often get such communication from companies these days so the reps on these forums are immensely valuable.
I strongly suspect that what we have here is a 'moan' with which a lot of us here should sympathise. Let me explain: "Oh, you do computers? I've got this laptop/typewriter/DVD/washing machine that doesn't work.....". Sound familiar? I've even had my mum say to me "You know about plumbing, don't you?!" No mum, I work in IT. I would hazard a guess that Mike has had this problem and had a run of dodgy AIO's interrupting what little down time he probably gets and is somewhat irritated by it. If you can't have a moan amongst friends, what hope is there?!
AIOs are a compromise, we all know this. They are produced to a price point that you cannot match with bespoke components and that is their appeal - I have one myself for this reason. They are great for their price but compromises have been made in their design partly as a result of the price point and partly as a result of the technical ability of their target market - they have to be maintenance free. Can you imagine what would happen if they told the average computer user to pour coolant in their computer to top it up?!

All this is fine as long as you don't expect the moon on a stick for your money.
I really don't think any deception or harm was meant so can we put away the torches and the pitchforks now please?