When you are in the public eye you offer yourself up for public ridicule. You can not be like Donald Trump and expect to be impervious to parodies and jokes. It also keeps them in check too. A lot of these public figures do outrageous things that need to be addressed and comedy is the best way to do that.
As the saying goes, sometimes you have to either laugh or cry. Our public figures have so much power, but that doesn't mean that they should be immune to joking or criticism. Parodies get people's attention by being funny, but they can also shed light on some very important political issues.
Yes, parodying public figures is a good thing. It is my belief that parody, when well written, can be a constructive means of critique. This is particularly true for public figures who hold positions of power. Parodies allow for dissenting voices to be heard and spread in an entertaining manner. Without parody, many members of the public, especially younger members, would be less engaged with politics in particular.
It is my belief that parody is a necessity to life. We take to heart celebrities, public figures and political figures all too often and using humor to balance out the serious side of these aspects is necessary to keep both balance and perspective. It helps to bring respect to person knowing that they can accept a joke about themselves as well.