I think the best argument for McMenno being scum is his play day 3 (which is particularly clear from the ISO).
He starts off arguing for no lynch (presumably based on theory arguments), then expresses a willingness to lynch anyone but Leonshade in #434
(despite the fact it's mylo; this is a response to a request for reads), then starts pushing Sgz for unknown reasons (he's pushing Sgz as strongly as he ever pushes anyone, and hasn't given any reason for Sgz as scum past #148
, way in the past and basically based on RVS posts). He also pushes Heartache as scum based purely on lack of claim
(presumably so that when Heartache claims, it gives him a convenient reason to revoke the scumread on his buddy, whilst getting in a bunch of distancing in the meantime). That's… all McMenno did day 3.
Heartache claimed a no-action on McMenno, and McMenno eventually claimed VT. That's a convenient set of claims for scum: it conveniently hides the fact that McMenno's been performing actions via providing corroboration. McMenno then pushed (and is still pushing) very strongly for people to believe that scum would trueclaim their role and fakeclaim their actions, and hasn't explained this even when asked. That makes a lot of sense from a scum perspective, because it would necessarily push suspicion onto me if people believed them; on the other hand, I can't see any reason to believe that scum would act like that in the first place, and suspect that there isn't one.
Then today, McMenno's been refusing to engage, instead trying to rush the day as much as possible. That makes it look like he's confident of winning if people don't think things through, but worried about what might happen if the day goes longer. #719
is a naked vote on me as soon as it looked like my wagon might go through. When a player hammers like that, it's normally considered an admission of being scum. That wasn't a hammer, but I'd have expected a townie to give at least some explanation.
PEDIT: My chart there was attempting to eliminate players as scum based on theory reasons (for example, we know that Sgz and Heartache can't be scum together). When I started it, I assumed that most pairs would be eliminated and we could solve the game on night actions (especially as the theory posts in the game so far, from McMenno, had been painting it as very simple). It turned out there were a lot more viable pairs than I thought.
It's a mathematical fact that based on the information we had on D4, in most of the pairings where you were (hypothetically) scum, you had a roleblocking role of some kind. (McMenno couldn't have blocked Leonshade N2 because Heartache claimed to tracked him nowhere and would have been town in the scenario of you + McMenno; Sgz couldn't have blocked Leonshade because I blocked Sgz; and Leonshade wouldn't have been able to rolestop himself
N3, so he would have needed a buddy to do that.) That wasn't intended to throw shade on you. It was intended to make sure that we weren't missing any possibilities as to who the scumteam was, that might have wrongly lead us to think that scum was confirmed or that a townie was confirmed scum. (And doing that was particularly important, because McMenno was trying to convince us of incorrect theory conclusions at the time!)