What does Orwell mean when he asserts, "But if thought corrupts language, language can corrupt thought"?
When the writing or speaking process begins, it is a formation of one's thoughts. The modern style of writing has become a one that uses superfluous words, worn-out phrases, and jumbles of stale sentences that provides no vivid picture. Orwell is saying that it is not only individual thought that can abuse a language,   but also the language could corrupt individual thought. The language style that is popular today is producing writers with a lack of  true communication. In fact most work ends up confusing a reader because it is very unclear. People are always trying to sound extravagant without even asking themselves what they are trying to say. Instead of true expression their writing turns into a bundle of vague, long and meaningless words. Because of the popularity of this style, the English language is decaying. It is losing the purpose of language which is to convey one's thoughts. Now language is becoming inadequate to express thoughts. Therefore, the shortcomings of language is what leads to the corruption of thought.

George Orwell the writer of Animal Farm discussed his concerns on modern writing in  "Politics and the English Language"