ideologically, the stance of being pro-black means
very little. so of course anyone can claim it.
tangible works directed toward black progress are the most telling of one's status as being "pro-black". choosing to build a black family, accumulate wealth that can be based down to generations of black people, and raising black children in a stable, two parent household with adequate resources is probably the most commendable example of being "pro-black"
of course, you could be pro-black through means of philanthropy for example, but statistically, the vast majority of people won't accumulate enough wealth to influence on a large scale.
as for your second question, white people have literally had centuries to acquire generational wealth, which has yielded control in every possible industry, and by that, fostered a system of white privilege where they can maintain control despite being incredibly individualistic. this rejection of marriage en masse is also a relatively new phenomenon... also, the high incidences of divorce states that people also tout to reference the shifting ideas on marriage has also been debunked...
http://www.nytimes.com/2014/12/02/upshot/the-divorce-surge-is-over-but-the-myth-lives-on.html