Shakespeare’s speaker defends a hard-edged position: being genuinely “vile” beats being falsely slandered, because the innocent still lose the private satisfaction of their own conscience once outsiders’ opinions take over. He questions why corrupt onlookers should greet his natural, lively blood with either praise or blame, and why people even more frail than he is spy on his faults and twist what he considers good into something bad. The poem pivots on a defiant “I am that I am”—a refusal to be defined by others. He argues that his critics are merely reckoning up their own abuses; he may walk straight even if they are bent. Their foul imaginations cannot dictate the meaning of his deeds. The closing couplet sharpens the point: unless they insist that all men are corrupt and proudly rule in that corruption, their judgment has no ground. The mood is bristling, self-assured, and darkly ironic.
Sonnet 121: 'Tis better to be vile than vile esteem'd — Summary
'Tis better to be vile than vile esteem'd, When not to be receives reproach of being; And the just pleasure lost, which is so deem'd Not by our feeling, but by others' seeing: For why should others' false adulterate eyes Give salutation to my sportive blood? Or on my frailties why are frailer spies, Which in their wills count bad what I think good? No, I am that I am, and they that level At my abuses reckon up their own: I may be straight though they themselves be bevel; By their rank thoughts, my deeds must not be shown; Unless this general evil they maintain, All men are bad and in their badness reign.