Sequels absolutely can affect the integrity of the original by expanding the universe of the plot in ways that it's original design never intended or the way it was originally perceived.
If you think that some new works expand the universe in a stupid direction, there's no reason you can't pretend they don't exist and still derive the same meaning from your favorite works.
Disney does this as a matter of policy.
Countless Shakespeare productions and remakes and reinterpretations don't diminish the original form.
That statement does nothing but detract from the conversation. Of course I'm not obliged to pay attention to any of them. I'm not making the generalization that all sequels are bad.