And that's a reasonable reaction. Get pissed. Shame him publicly. That's all that needs to be done.
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Okay back up. Getting groped is sexual assault by law, but sexual assault covers an immense range of interactions and getting groped is definitely on the mild side of the scale. Don't try to make this seem worse than it actually is by applying legal terminology.
The idea that the confidence of the 'attacker' (again, poor word choice, so let's say 'groper') is what gives people trauma is less of a justification.