I too feel that he needs to pay his dues, but that's a coaching error, not anything to do with Sam himself. Drawing on my own team for an example, our current top receiver S.J. Green didn't have his spot handed to him. He spent some time on the practice roster, played sparingly in his first season, platooned with Ben Cahoon in his second full season, before taking over Ben's spot full-time last year.
And for what it's worth, Fantuz hasn't been particularly impressive as a Cat so far. My abiding memory of him from last night's game consists of the penalties he took (offside and illegal block down field). I'd say if you're going to pile on a receiver, pile on Fantuz. He's a veteran, former league leader, and he's getting paid a hefty chunk of change.