Umm, dumb arguments. I agree you could say well if its this position then I want any position, but I don't think that is what OP is talking about. Its very reasonable to have a CB returing punts or kicks, because it happens in the NFL every week during the season, probably pretty much every week there are some CB's returning punts, if not multiple games.
They naturally have the skills needed to do it well (agility and field vision/quick reaction time etc.) Also many NFL teams are now recruiting former WR's to play CB (Richard Sherman etc.) so CB's are VERY similiar to WR's and can be used interchangably to some degree, so there is no reason to give WR and HB return skills, but not give them to CB.
I would not however worry about it being extended to Offensive Guards, because no Offensive Guards are returning punts or kicks in the NFL. CB's do it every day during the season, and some are better then HB's and WR's at it because they all have a similiar skill set.
So, bottom line, yes CB's should have more return options. Pretty simple. I don't see it as a big deal, but OP is absolutely right in his point.