Many great points and views already brought up here, but I personally feel that native species should always have conservation priority over non-native ones if their population is threatened, even if I enjoy targeting and cacthing the introduced species. For example, I feel that Lake Trout and Ciscos in the Great Lakes should be the priority in conservation over introduced Pacific Salmonids and Brown Trout. As I said, I enjoy catching them all and Salmonids are my favorite group of fish, and even though Lakers are my overall favorite, more importantly they're the native species in this situation so they deserve the most protection.
Another example of this would be stocked Trout. Where I live, my local creek is a trophy Northern Hogsucker fishery that also produces very nice White Suckers and sustains a small (in size of fish) resident Smallmouth Bass population. This creek is stocked with Rainbow and Brown Trout several times each year which undoubtedly consume the fry of these species in addition to the smaller native forage species like Minnows and Darters. I love catching these Trout, Suckers, and Bass, but believe that the populations of all of the native species need to be monitored to ensure that stocked trout do not threaten them to the point of extirpation or where the ecosystem would be disrupted.
In both of these cases, it is not always black and white, or native versus introduced/invasive. With enough management from fishery organizations and the public, it's very possible to find a balance where the native species that have a right to inhabit their home waters (whether game, coarse, or forage) thrive alongside introduced sportfish that provide additional fishing opportunities to the public and many times support local economies.
Now, in terms of showing others the value of native roughfish like Gar, Bowfin, Drum, and Suckers, some things I'll often do are explain the role and niche these species fill and take others fishing for them. My dad used to absolutely loath catching FW Drum while fishing Lake Erie for Perch. But when I started fishing I quickly became obsessed with catching the lowly Drum. Now, after many years of educating him and showing him how hard these great sportfish fight, he enjoys catching them almost as much as I do. So the next time one of your friends catches a roughfish and complains about it, show them how valuable they can be both to the environment and as sport.
My two cents.