from what I recall of that vid, I think what prompted that remark by Ian was his desire to quickly but tactfully intercept Larry, who IIRC seemed to be on the verge of veering off into a full-on “slot some floppies” rant.
Anything pertaining to Rhodesia on the internet is bound to draw in the worst of both the pro- and anti- sides.
I think that Rhodie FAL vid was the only one that Ian ever shut down comments on.
I doubt Larry and Ian have much in common beyond a shared enthusiasm for guns, but that’s enough for them to collaborate and talk shop (I also believe Ian bought his FAMAS from Larry).
I can’t imagine Karl interacting with Larry for very long without it turning awkward or hostile.
Karl probably already hates him anyway, much like he hates most of the rest of the YouTube gun channels.