Nobody ever criticised the results he gets (or if they did, they shouldn't), just that they didn't like the way he got those results and felt that the race would have been better had he not been there. A lot of riders have been criticised over the years because fans, or subsections thereof, didn't like the way that they got those results because they felt that whether or not the rider's tactics were the right choice to maximise their own results, they were detrimental to their enjoyment of the race, so they dislike the rider regardless of the efficacy of their tactics. A lot of the time fans know why a rider is employing a particular tactic, but it doesn't mean they have to like it.
Durable riders with a strong sprint often get the brunt of it because of the style of racing; people don't tend to go into sprint stages with expectations of excitement, so while pure sprinters may not be the most popular of winners among the purists, they don't seem from my readings over the years to arouse the same antipathy as riders who sprint after hilly races, because usually fans have higher expectations of excitement in those stages and so when moves are neutralised and a sprint ensues (whether a flat sprint after hills, or an uphill 1km shootout on an unselective mountaintop or a puncheur finish), they tend to perceive that more negatively.
If a rider has the ability to win races in that fashion but varies things up, people will be more forgiving - take Peter Sagan, for example. Sometimes if he needed a win and the best way to win was to sit in the bunch in one of those stages that burn off the pure sprinters and then outsprint the non-specialists in a really dull stage, it's what he would do, but people wouldn't get frustrated at him doing that the way they did for a Simon Gerrans or to a lesser extent Michael Matthews (who started to vary things up a lot more later in his career), because Sagan had multiple other ways to win or podium that he would employ with relative regularity (rather than as an occasional exception). People would likewise be very dismissive of Alejandro Valverde as somebody who had that patented defensive "win the sprint at the top of the hill" style for much of his career; he would come out of his shell from time to time, but it would often be in much smaller races and when it came to racing against the elites he'd go right back to his usual approach. Valverde did have those other weapons - and employed them - but the way he did it and the way he would seldom do it in races where it actually mattered meant he would be perceived more negatively.
In the continuum of "riders who can win sprints after stages requiring durability" in terms of the entertainment they bring to races, with, like, Bettini or Sagan at one end and Gerrans at the other, Pedersen belongs somewhere roughly in the middle for me. I can see why somebody who places him further towards the negative end of that continuum views him negatively, but personally I don't. However, that's more because in all honesty, although he's been one of the top ranked riders in the world for over half a decade, a former World Champion, and five monument podiums, he just doesn't arouse any strong feelings in me, positive or negative. I don't think "oh, this race would have been better with Mads Pedersen in it", but neither do I think - as some here clearly do - "man, this race was made worse by having Mads Pedersen in it". But that's because by and large I just don't think of Mads Pedersen at all.