So it's fine to mess with them, even illegally, just because you don't like them?
* convinces people to willingly provide personal information
Convincing is not forcing, and in fact, you say "willingly" yourself. Any business convinces you to willingly give them money or other value.
* sell at ridiculously high prices
To respect to what? Prices are determined by the market. We are not talking about a life-saving medicine or health care, on which there could be some debate.
We are talking about a company selling information, which has value and which it acquires through an infrastructure that takes a lot of money to run. Value that customers are willing to pay for.
* Even if you are legitimately using LinkedIn as an end-user, it’s easy to get blocked
For what definition of legitimately? Yours? Since it's their business, they can define what is a legitimate free use and what can be a paid one.
* They are not a social network
So based on what I pointed out, they are not a social network only because they are not free? Do all social network have to be free and give your data for advertisers to be social networks?