This is what happens when you don't think of the consequences of your actions. It might sound unfair to you but this is a precautionary measure to ensure the community is spared the risk of exposure to frivolous offers.
Asking for a loan of USD 4000 and offering to secure it with worthless collateral was a reckless attempt to put certain naive people here at risk of parting with their bitcoins. Thus the red paint.
Always think before you type.
Can you please tell me what kind of collateral i need to provide to prove that i am not a thief or scammer
It would be wised, to read the stickies that exist at any section of the Forum. Especialy when the section is about Lending.
Here is your answer :
https://bitcointalk.org/index.php?topic=577765.msg6311902#msg6311902Collateral doesn't "prove" anything except the fact that you will think twice to Default a Loan.
It's a safety net for the Lender not to loose his funds, to cover him in a possible Default from Borrower's side.
Read this stickie and then read all the rest as well. You will get the answers that you seek, thank's to the members that wrote them.