Assigning the same variable from different untrusted sources like request parameters, session data, etc. in Go code can cause confused logic and vulnerabilities. The variable may end up with an unintended blended value from overlapping disjoint sources. To avoid inconsistent state and logic issues, variables should be assigned from a single trusted authoritative source. Consolidating assignment to one clear source of truth ensures code operates on the intended value, avoiding blended state from multiple unvalidated sources.