What bubble are you in that it comes as a surprise that not every black supports BLM?

Every black person did not support Barack Obama.

Edit to add:
 
Being a Black Conservative and especially a Trump supporters is not a popular opinion.

However, Black Conservatives labeled Black Democrats as having a slave mentality and of being on a Democrat Plantation 

A closer look at the phrase “Democrat plantation” and the divisions that accompany it, however, make clear much of this rhetoric is shallow and ahistorical. It distorts the current state of the relationship between Democrats and African American voters, and deprives the latter of agency, in part because of a failure to adequately understand the historical comparison that this rhetoric purports to make.

Historian Leah Wright Rigueur, author of “The Loneliness of the Black Republican,” noted that black Republicans criticized the plantation politics of the Democratic Party as early as 1964, inspiring white conservatives to occasionally deploy the phrase to critique liberals. They spread the plantation trope throughout print media in the 1970s and 1980s, eventually helping it gain mainstream attention in the 1990s.

Author and political pundit Armstrong Williams was arguably the most powerful purveyor of the phrase, promoting the notion that the Democratic Party had betrayed black voters for three decades. But the plantation trope was appropriated by others, including a local white columnist and radio host in Denver named Mike Rosen; the Log Cabin Republicans, a conservative LGBT organization; and Louis Farrakhan, who notoriously leveled “fierce jabs” against Bill Clinton in 1996. He claimed the Democratic Party’s leaders failed black Americans and that anyone inclined to support Clinton were “slaves sold out to the Democratic plantation.” Unlike black conservatives, Farrakhan’s solution was a third-party candidate who could deliver on campaign promises through their exclusive commitment to black voters’ collective interests.

https://www.washingtonpost.com/outlook/2019/01/08/how-democratic-plantation-became-one-conservatives-favorite-slurs/

You don't let the slurs define you. 

Edit to add:

They are approaching things from a U.K. standpoint, but it mimics arguments in the US.

The Henry Jackson Society’s Black Lives Matter UK anthology provides a platform for some of those voices.  Its authors — who prioritise cohesion over difference — set out practical and realistic paths to improving community outcomes and healing social divisions in Britain.

Binding their contributions together is a belief that hard-left identity politics – much of which is culturally imported from the USA – threatens to weaken domestic race relations and destabilise Britain’s multi-racial democracy.

https://henryjacksonsociety.org/publications/blacklivesmatter/

The arguments are similar to those used by Conservatives against Black activists in the United States. So-called identity politics will destabilize the country. They are a danger.