You’ve written a good correction on this topic by pointing out how important it is to understand offense in individual terms instead of purely group-dynamics. But I’m a little confused on what you define the microaggression paradigm to be. The piece you linked to written by Jesse Singal does list five core assumptions per Scott Lilienfeld’s writing. Number two in particular says:
“ 2. Microaggressions are interpreted negatively by most or all minority group members.”
So by your own links of choice on the topic, I do think your summary of microaggressions as merely
“ the notion that these things cause harm to some individuals.”
is rather inaccurate. I don’t think your piece here completely falls apart, since there are limits to opinion polls when discussing individual offense. But given the microaggression framework does extend beyond mere individual offense, your critique of Conor Friedersdorf’s article is rather stunted by your own choice of linked arguments.