The phrase "offensively lazy" is somewhat tongue-in-cheek. Obviously no one is "offended" by lazy humor the way they are by racist humor, etc. It would more accurately be phrased "annoyingly lazy".
And I agree that this Nickelback joke is annoyingly lazy. Not funny enough for the inconvenience it apparently causes some users.
I think "annoyingly lazy" is a very fair description.
"Offensively lazy" annoys me because I don't think it is tongue-and-cheek much of the time. I think it is a phrase that gets brought into the fray when a joke really was offensive to some people. I never hear it in response to "rated PG" jokes; people who say it probably are offended, but it seems they have misidentified the source of their feeling of offense.
And I agree that this Nickelback joke is annoyingly lazy. Not funny enough for the inconvenience it apparently causes some users.