Historically the rationale for pro-business policies is that greater production creates more wealth for everyone in a society. As a result it could be argued that a labor union might hurt an economy if less output comes from the same input, while those labor unions' arguments would be that they disagree about how different working conditions maximize the society's actual utility.
A non-compete on the other hand is a contract to decrease worker productivity. It is the opposite of union agreements that forced companies to employ people whose work is no longer needed, it is an agreement not to work. Furthermore, it isn't even entirely about benefiting business owners over their employees, but about benefiting established companies for their past success rather than whether or not they can compete in the current business environment.
I don't think that's really true, in a realpolitik sense if you look into why different interest groups were advocating for "pro-business" policies at various points in various countries' histories. Historically the rationale for "pro-business" policies has most often been that they increase the profits of businessmen, which is why parties mainly representing the business sector have advocated for them. Sometimes they produce more wealth for everyone in society, sometimes they reduce it, other times they're roughly wealth-neutral but just reallocating it. But that isn't the point or the parties' raison d'être, though they may pretend it is in their politicking.
It does capture why I am surprised that content distributors have lobbied against ISP favoritism. I want to believe that Netflix wants an entrepreneurial environment like the one that enabled their initial growth, but I can't help wonder if their greatest threat isn't some new upstart, and why they wouldn't be in favor of a large barrier to entry, even if it costs a nontrivial portion of their revenues.
I have to imagine they are choosing a sizable chunk of a much larger pie instead of the vast majority of a tiny and shrinking pie.
However, while it may often require some credulousness, I think a significant majority of people sincerely believe that their political positions make the world a better a place rather than just their own lot in life.
There are honest discussions that can be had about most policy decisions. For instance, it might be difficult to sell your software business, if you can't legally promise not to immediately launch a competing product. And yet, most of the serious policy mistakes of the past few decades have been made in the wake of debates involving two sets of competing soundbites—a problem that could be improved by better economic education starting at a younger age if I'm right that people are generally motivated to improve the world.
It is relative, if you are big and established they are good, if you are small/medium (where most innovation and eventual businesses comes from) then they are bad.
It is anti fair business, but in a monopolistic/feudal/plutocratic type system it might be pro-business to own skilled people (anti-poaching agreements are also pro-business in that view). In a libertarian and free market sense it is anti-business when viewed from the aspect of an individual/small/mid company.
I guess its safer to say non-competes are pro big business and anti small business / anti innovation at least.
Beyond them, it's negative-sum.