You seem to be saying that "the right may be more likely to resort to guns" has "no base in reality". That would surprise me, for two reasons. First, gun culture seems to be much more prevalent in parts of the country that lean right. Second, the topic was mass shootings, and there have been several prominent mass shootings lately that have been done at least in the name of the right, whereas the Dayton shooter is the only one that I know of that was claiming positions of the left.

Neither of those are hard data. On the other hand, you seem to be the one claiming that what "most people know" is wrong; do you have data?