Are blockchain-based transactions easy for money laundering?
Money laundering is illegal so this is not advice nor endorsement. Bitcoin transactions are not particularly good for large scale money laundering. You have to obtain bitcoin without leaving any personal trace and then sell it with an appearance of legitimacy. I am sure there are ways, but it is not that good.
I don't even know why people are trying so hard to attach money laundering to bitcoin because just like other fiat currencies you can not determine how one should use his money and so if they use it illegality it is up to the system to apprehend them rather than blame it all on bitcoin.