No, it is not semantics Randomly Me.
Saying “if your skin is white, you are a racist” may be inflammatory, but that does not make it wrong. And I have to be honest, I have very rarely heard the message said in that specific way. More likely, I hear people infer, through various statements, that to grow up white in a North American society that is both institutionally and culturally white supremacist, one cannot help having those beliefs ingrained throughout their development. If you are able to take a step back from making it all about you being called a bad name, what is being communicated is that holding ingrained and largely unrecognized beliefs that support racist structures does not make you a bad person, it makes you a normal person who is reflective of the world in which they live.
As to “if you use the term all lives matter you are a racist asshole” … in 2016, after the amount of times this has been explained, I would concur with that statement. Why? Because frankly, context is everything. And the context in which “all lives matter“ is being used, is in refute of “black lives matter.” A slogan specific to push back against the systemic and institutional racist abuse of a large number of the population which law enforcement has been entrusted to serve. THAT, is what makes the “all lives matter” statement problematic.
Let me try it this way. It is akin to a man entering a rape support forum for women and complaining that men are raped, too. While that statement is indeed accurate, the intent is a tad disingenuous, isn’t it? Because it’s not about male rape victims, instead it’s about disturbing and silencing the theme of the moment, that being female sexual assault at the hands of men.
So, given the context, and the repeated examples of police aggression, abuse, and murder of unarmed black citizens, yes, saying that “all lives matter”, is a racist thing to say.