I'll even add to the counter-argument: "Well, if the right is not exercised, we will lose it!" Similarly, my signature regularly reads, " keep our founding fathers' visions and rights for this country pure," so did their vision only include hand-guns?
This is true, a right needs to be exercised, and obviously the forefathers did not imply only "handguns" or carrying a certain way. However, instead of randomly strolling the street with a long-gun, leaving citizens (including pro-2Aers) distressed and confounded, there are more responsible ways to exercise the right.
As previously discussed: The practicality to carry a long-gun daily is not present. Thus, there will naturally be alarm. Because the practicality to carry for defensive purposes is very present in our society, and should be commonly accepted, it's more feasible identify law-abiding citizens with a holstered handgun, and coach "gun grabbers" to expect such.
Exercise the right irresponsibly, and it gives the "gun grabbers" more "ammunition" to pass paranoia based, ineffective legislation.
You already agree there is no practical need for you to carry a long-gun daily. Yet, it's essential to exercise the right. So, instead of encouraging others to gallivant down the road wielding a long-gun, why not organize a structured, long-gun OC march? Thus, the right is being exercised responsibly.
But to directly answer your question: You should care that the arms are beared responsibly because you want those rights to not be inhibited by unconstitutional legislation, conjured up by gun grabbers, and justified by irresponsible exercise of the right.