There are a number of people who do not respect Charles as a man or future king if you read the comments on papers like the DM.
I actually think that there is an increasing attempt to get public opinion to reach the stage whereby Charles never becomes King with the ongoing attacks on everything he does e.g. the current demand to see the letters he has written to ministers and the condemnation of his buying of the house in Scotland.
Yes, I see that campaign against Charles too. I think what the media is trying to do is attack the royals over and over and over again until the impression stays in people's minds. For example, if the press calls Charles eccentric or out of touch often enough, even if they re-hash the same couple of facts each time to prove it, that's how people will view Charles. After awhile, even when people run into a balanced news article about Charles, they won't read it in full because they'll just think, "Oh, Charles, that doddering fool again." I think papers like the DM are exploiting this technique to the full, because they know that especially these days, people aren't critical readers or thinkers. And with the economic crisis, people are looking for an excuse to blame the rich and privileged for the world's problems.
Fans of the BRF shouldn't think that just because the royals have always been respected by a majority of people in the past, that they will continue to be respected. I'm sure that at one point in French history, people expected the monarchy to last forever. But the death knell of a privileged class is the moment the ordinary people start to experience real hardship, and then see the upper classes carrying on without a care in the world. If the world's economy doesn't recover, we'll probably see more and more of this in the world--people starting to really resent the upper classes for their comparative privilege. Especially if the media continues to fan the flames of resentment.
So I do think William has to be careful. He can't be complacent and think that he can do whatever he likes until he reaches his mid-30s, because his lifestyle is already out of touch with people of his own generation. I think the monarchy has to be somewhat relatable to the average "commoner", in the sense that they see the family life of the monarch as something they would aspire to themselves. I think this is why Queen Victoria with her large family was respected, and later King George VIII with his tight nuclear family, because they epitomized the ideals of the day. And it's why people lost respect for the monarchy during the 1980s and 1990s because of all the divorces in the younger generation. It isn't that members of the British public weren't getting divorced themslves, but they wanted to see members of the monarchy holding up a higher standard.
As far as William and Kate go, I don't think it's enough anymore that they get married "someday" and have a stable marriage. I know plenty of people in their late twenties who are not married, but they seem to fit one of three patterns: they are single and haven't found the right person; they have been dating someone for a long time but are completing higher education and preparing for high-powered careers and won't marry until they graduate; or they are living together and even having children together because they don't see marriage as important anymore or are waiting until they have enough money to afford it. William and Kate, especially Kate, don't really fit into any of those boxes. They aren't avoiding marriage because they can't afford it or because they are still in school (I don't count William's military training) or because they don't know each other well yet--the appearance is that they're avoiding it because they don't want to take on public responsibilities. I find that hard to relate to, especially with Kate. Many girls her age are waiting to marry, but most are doing it because they are actually still in school or building a career. Kate, on the other hand, hasn't made any ambitious career moves, but she's still guaranteed a life of privilege and wealth someday if she marries William. I think that's where the "Waity Katie" title could become damaging to her...if people her own age start to resent Kate because they are finding it hard to get jobs, or are going through years of education to get good jobs, while Kate is going to have wealth handed to her on a platter if she marries William.
If Kate and William were quietly married and doing a few royal duties, I think the press would still criticize them, but at least Kate would appear to be contributing to society.