The default Rails way of using Activerecord will automatically sainitize inputs for you. Not turning it into an associative array doesn't add anything to security.
User input need to be sanitized always. Rails make it easy and is the default way.
There's nothing stopping you from passing unsanitized params to the database. I.e. where("name LIKE '%#{params[:name]}%'") instead of where("name like ?", "%#{params[:name]}%"). While the 2nd option is definitely the recommended way to do it, there's nothing stopping you from doing it the wrong way, and I bet many do.
The thing is, it's easier to do it the right way. It requires a special, deliberate effort to do it wrong. That seems like a reasonable implementation of a "magic" feature. PHP, as usual, gets it exactly backwards. It's easier to do it wrong, and requires a special, deliberate effort to do it the secure way.
Yeah maybe. Depends on the person I think. I actually find it easier to assemble a SQL string myself. If you're new to rails / AR and you're not familiar with SQL then you'll look up and figure out how to assemble the SQL via the ORM methods. If you're new to rails but an old hand at SQL, just building the string is super easy and takes you 2 seconds without looking up any documentation. Of course assembling the string AND sanitizing it requires a heck of a lot more effort.
Regardless, it's not a knock on rails. Just saying it's not necessarily a magic bullet to secure apps (and I don't believe rails nor PHP needs to be).
All true. I was thinking of the submitted link still. Manually sanitizing instead of having something doing that for you is a bad idea because you will forget.
User input need to be sanitized always. Rails make it easy and is the default way.