Sign language allows

A.I.'s comments (provided by poe.com - Assistant):

This haiku cleverly explores the expressive power of sign language, particularly in the context of conveying strong emotions, such as anger or frustration. The phrase 'silently loudly' is a striking oxymoron that captures the essence of how sign language functions. While the communication is physically silent—without spoken words—it can be incredibly powerful and expressive, conveying intense feelings and meanings with just hand movements and facial expressions.

The juxtaposition of 'silently' and 'loudly' suggests that the absence of sound does not diminish the impact of the message. In fact, it highlights how body language can often communicate more forcefully than spoken words, particularly when it comes to cursing or expressing strong sentiments. 

The haiku's playful tone, juxtaposed with the idea of using sign language to 'curse with the worst words', adds a layer of humor and irony. It reminds us that language comes in many forms, and sometimes the most potent expressions of emotion can be delivered without a single spoken word. Overall, this haiku encapsulates the richness of communication beyond verbal language, inviting readers to appreciate the nuances of expression in different forms.