The implication is that liberals are engaging in soft bigotry of low expectations. That they are pandering to black voters for power.
Another implication is that all the things that liberals are promising to the minorities that should be helping black people, such as welfare and affirmative action, end up causing more harm in the long run.
Of course, I expect you to ask why? I would say one part lust for power, one part good intentions that pave road to hell and one part good old fashioned ignorance.
And if you ask about motive? Just a power grab. In contemporary culture diversity is much relished. But not all of it, diversity of opinion is being shunned and anybody daring to show doubt is ostracized. If you take a long hard look - pretty much all the power structures on the west are very, very liberal/progressive (entertainment, media, school system, government and indeed politics).
Since the consensus is that expanding government outreach and bringing more and more functions of society is a good thing and since the results are really not there - the liberals would either have to face their folly or instead keep doubling down.
And since doubling down makes things worse - the liberals are becoming increasingly authoritarian, thus the vicious cycle is feeding itself.
p.s.: In case you were asking what the motive of BLM is? I don't think they have one. Just as any other flavor of identity politics they are engaging in an us vs them discourse, which inevitably will cause them to turn on themselves. But liberals are going to squeeze as much out of them as possible.
