An interesting verb to use when discussing writing and argument, "vitiate" allows you to vividly describe how certain aspects of a text or elements of an argument weaken or corrupt that text or argument.
"Frequent and confusing verb errors vititate the emotional and philosophic power of her essay."
"The unspoken assumption that we are all willing to sacrficice for the benefit of others vitiates Johnson's hopeful arguments about immigration reform."
Of course, this verb offers a prettty harsh critique of whatever you apply it to, so use vitiate wisely lest you vitiate your audience's trust in your judgement.
