It's not because you have no regrets that it's ethical. Even if it's a company like LinkedIn that makes it hard to unsubscribe, your input pollutes the anti-spamming algorythms with semi-legit emails. There are clearly millions of people who are fine with getting LinkedIn messages, and you're just being an ass, like putting your half-eaten burger into the recycling bin because the garbage bin was further out. Someone on the other side of your transaction is going to be tasked with taking your now-rotten burger outside of the recycling.