chew
Explanation
This comic takes the famous action movie one-liner "I came to kick ass and chew bubblegum, and I'm all out of bubblegum" (originally from the 1988 film "They Live" starring Roddy Piper) and subjects it to formal logical analysis.
The bearded character delivers the classic line, and then a second character (wearing glasses) points out the logical implication: "Therefore it is impossible to kick ass AND chew bubblegum" -- because if you are out of bubblegum, the conjunction of both activities cannot be satisfied. The first character then tries to correct himself: "I should have said 'I came to kick ass XOR chew bubb--'" before being cut off with "Stop! Stop it!"
The caption reads: "I became insufferable after learning first-order logic."
The humor mechanism is the application of formal logic to a domain where it was never meant to apply. The original movie line uses "and" in its colloquial English sense (meaning "in addition to"), but when parsed through formal logic, the "AND" operator combined with the constraint "no bubblegum" creates different logical implications than the speaker intended. The character's attempt to fix the statement using XOR (exclusive or) -- meaning exactly one of the two activities but not both -- is technically more precise but completely kills the macho spirit of the original line.
This is a classic SMBC joke about how learning a little bit of formal logic or mathematics can make a person unbearable in casual conversation, insisting on precision where none was needed or wanted.