Membership of the United Nations gives every member the right to make a fool of himself, and that is a right of which the Soviet Union in this case has taken full advantage.

Meaning of the quote

This quote means that being part of the United Nations allows any country to act in silly or foolish ways, and the Soviet Union has taken advantage of this right. The speaker is saying that the Soviet Union has used its membership in the United Nations to embarrass or make a fool of itself. The core idea is that being part of the UN gives countries the freedom to behave in unwise or ridiculous ways, which the Soviet Union has done.