Showing Deadpool explicitly cutting and shooting down bad guys, like on those "PG-13 comics" (the content is rated WAY differently in comics, but let's follow you on this one for a moment) would've had to be toned down had the movie been PG-13.
You know, all those wonderfully bloody panels of him killing people or hilariously gory scenes in which his regenerative powers are most needed.
And that's all I have to say on this. You have your own opinion and that's fine. But don't try to sell it as a fact, stating that they got the character wrong and TURNED him into an R-rated one.