How we cite our quotes:
They rightly do inherit heaven's graces,
And husband nature's riches from expense; (5-6)
After all that hoopla in quatrain 1 about the mysterious coldness of the powerful people, probably the last thing we were expecting was to hear that they "inherit heaven's graces"—not to mention that they do so "rightly." If the speaker had just said they "inherit heaven's graces," we might have taken it as a statement about how "the rich get richer"—this time changed to "the powerful get more powerful." But by sticking that "rightly" in there, he makes it sound like he approves of the whole thing. Why do you think he would say this?
They are the lords and owners of their faces,
Others but stewards of their excellence. (7-8)
These lines paint a striking picture of the powerful people: they are "lords and owners," and all other people are nothing but "stewards" (that is, servants). So is Shakespeare's whole poem simply in praise of people who are higher up on the social hierarchy? We don't think so. Take another look at what "they" are "lords and owners" of. That's right: "their faces." Similarly, when we look at what the "others" are "stewards" of, we see that it is something very abstract: "their excellence." So maybe all the other poor schlubs just help make the powerful people more "excellent." From this, it looks like Shakespeare is using the language of ownership and servitude as a metaphor for internal differences in people's personalities.
But if that flow'r with base infection meet,
The basest weed outbraves his dignity. (11-12)
So who's laughing now? Bearing in mind that the "summer's flow'r" here is probably intended as a stand-in for the powerful people we learned about in the poem's first quatrain, it suddenly looks like those tough guys aren't really so tough. One little infection and the "bases weed outbraves" your "dignity"? That makes the powerful people sound pretty fragile (as if being compared to a pretty flower didn't already) if you ask Shmoop.