He dislikes proselytizing his religious beliefs to others at parties.

proselytizing 是动词 proselytize 的现在分词形式。proselytize 由名词 proselyte（改变宗教信仰者）加上动词后缀 -ize 构成，意思是"劝人改变宗教信仰"或"积极宣扬某种信仰"。现在分词形式在这里表示"进行劝诱/宣扬的行为"。