Is it rude to be direct to the Clients/Customers? Does it mean showing attitude?

Being direct to a client in a polite manner will reassure the client that you are objective  and open minded . This open mindedness will help the client to respect you as long as at the time of being direct , you are within the correct context .

NO. As long as your directness is not personal and is positioned politely and professionally. The saying is 'the customer is always right' which in my opinion is absurd and ridicules....if the customer is the cause of a problem it clearly needs to be addressed and if that involves telling them they are wrong...so be it! ....but just do it in a polite and correct way without making it personal.

It's depending on the customers type but we have to be honest and polite, because the customers always right.