Synonyms for Besmirching:

v.

•dirtying (verb)
soiling, Tainting, contaminating, Streaking, Fouling, Defiling, Muddying, dirtying, staining, Polluting, Smudging, smirching, Putrefying, Befouling.
•slandering (verb)
Defaming, blackening, Denouncing, Maligning, Traducing, Vilifying, badmouthing, Slandering, Besmearing, Scandalizing, Pillorying, Smearing, Dishonoring, Sullying, Calumniating, Detracting, Discrediting, Stigmatizing, denigrating, Libeling, Tarnishing, Shaming.