It's really interesting, because the addition of Ads is not wanted nor in any way beneficial to the consumer in this transaction, it just happens to be part of the business model of the seller that he now seeks to protect.
Would the same apply if I buy a printer and modify it to use 3rd party cartridges?
How about a company that could remove the addictive elements of cigarettes?
If you want me to provide additional revenue on top of the transaction, then enter a contract with me. Just because you made it "free" doesn't mean you must be legally allowed to force me into some other consumption...