Thanks for the clarification. I didn't mean to imply that LQG researchers had no interest in proving their framework to be compatible with Yang-Mills theory: that's obviously an essential test of any realistic theory of gravity! My intent was to share my impression that they generally weren't expecting Yang-Mills to appear "automatically" as a necessary component of the LQG formalism (much less for a specific group structure and matter content to be required by it). That's in contrast to string theory, which
does seem to fairly inevitably generate not just quantum gravity but also gauge theory by one mechanism or another. (And for a while, many or most string theorists were optimistic that a unique preferred background would turn up within a few years, too.)
I guess I'd say that string theorists I've known just don't think about LQG folks much. I've seen skepticism and some level of hostility, too, when there was an LQG talk in the department. But even then it usually came with a baseline level of professional respect. (Maybe I wouldn't say that so readily if I'd ever met Lubos Motl. There are always a few trolls, right?)
As you point out, quite a few LQG proponents talk about string theory rather a lot, and some even publish articles in which LQG proponent characters argue circles around straw man string theorist caricatures. (I read this one when it came out, as I recall. It made some good points, but it didn't go out of its way to portray the string theorist character as a decent human being, and the tone overall was just so damned smug.)