from Le Guin and then Stanisław Lem's wiki pages:
Le Guin refused a Nebula Award for "The Diary of the Rose" by withdrawing the nomination in protest of the Science Fiction Writers of America's revocation of Stanisław Lem's membership. Le Guin attributed the revocation to Lem's criticism of American science fiction and willingness to live in the Eastern Bloc, and said she felt reluctant to receive an award "for a story about political intolerance from a group that had just displayed political intolerance" toward communism.[11][12] She withdrew the novelette shortly before the announcement of the winners. The SFWA pleaded her not to do that since she had in fact won, but Le Guin insisted on the withdrawal.
Lem was awarded an honorary membership in the Science Fiction Writers of America (SFWA) in 1973. SFWA honorary membership is given to people who do not meet the publishing criteria for joining the regular membership, but who would be welcomed as members had their work appeared in the qualifying English-language publications. Lem never had a high opinion of American science fiction, describing it as ill-thought-out, poorly written, and interested more in making money than in ideas or new literary forms.[42] After his eventual American publication, when he became eligible for regular membership, his honorary membership was rescinded. This formal action was interpreted by some SFWA members as a rebuke for his stance,[43] and it seems that Lem interpreted it as such. Lem was invited to stay on with the organization with a regular membership, but he declined.[44] After many members (including Ursula K. Le Guin, who quit her membership and then refused the Nebula Award for Best Novelette for The Diary of the Rose)[45][46] protested against Lem's treatment by the SFWA, a member offered to pay his dues. Lem never accepted the offer.[42][44]
further interesting tidbits from Lem's page:
Lem singled out only one[47] American science fiction writer for praise, Philip K. Dick, in a 1984 English-language anthology of his critical essays, Microworlds: Writings on Science Fiction and Fantasy. Lem had initially held a low opinion of Philip K. Dick (as he did for the bulk of American science fiction) and would later say that this was due to a limited familiarity with Dick's work, since Western literature was hard to come by in the Polish People's Republic.
Dick alleged that Stanisław Lem was probably a false name used by a composite committee operating on orders of the Communist party to gain control over public opinion, and wrote a letter to the FBI to that effect.[48] There were several attempts to explain Dick's act. Lem was responsible for the Polish translation of Dick's work Ubik in 1972, and when Dick felt monetarily short-changed by the publisher, he held Lem personally responsible (see Microworlds).[49][48] Also it was suggested that Dick was under the influence of strong medications, including opioids, and may have experienced a "slight disconnect from reality" some time before writing the letter.[48] A "defensive patriotism" of Dick against Lem's attacks on American science fiction may have played some role as well.[48] Lem would later mention Dick in his monograph Science Fiction and Futurology.