A Slovak proverb (Kto sa chce bit palicu si najde.) Club in this case is referring to a wooden stick, not an association.
The general idea of this proverb is that if someone wants to pick an argument with you, he will find an excuse to do so, no matter how decent a person you may be.
Sir Thomas More comes to mind as a good example of a person who was particularly careful about not giving his opponents an excuse, yet was beheaded.
When I was a young psychologist in Slovakia, a famous psychologist, hated by the Communists, wrote a psychology book. Then a Communist ideologist wrote an article in Pravda (not the Russian Pravda, we had one in Slovakia, too) criticizing him and his book.
The psychologist I worked with commented on why the author was not more careful.
When I later had an occasion to meet the famous psychologist, I told him about the comment. He said it did not matter how careful he would be: If the Communists did not like him, they would always find something in his writing and twist it for their purposes.
Of course, the proverb is not about Communists (the proverb is centuries old), I am just using this as an example of what the proverb means.