We shouldn't have to, no. Ask yourself why you think it should be necessary to always explicitly talk about slavery whenever we discuss the US constitution.

Think about it this way: you don't rehash the rules of football (or "soccer", if you're from the US) every time you talk about a match. You don't go into the history of how those rules came to be what they are now. It's all part of the context and you only revisit that context when there's a reason to do so.

The relationship of slavery and the US constitution should be part of the context everyone is aware of. That means it should be part of education everyone receives. Thinking that it needs explicit mention in every discussion of the constitution implies a belief that most people aren't aware of the context, and that is a problem that needs a proper solution.