I wouldn't call it biased, but it is manipulative.
If you want to make a representive poll for anything, then you should avoid negative questions and your question definitely is one.
Asking if someone would be opposed to the implementation is manipulating the poll. The most natural question here would be "do you want this to be implemented?". I know, it's not your fault that people don't read the question properly, but that's how a good poll is made. Many people don't actually read the question and "assume" that you are going to ask if they want this implemented.
People like this will falsify your poll and it might look like you want to manipulate the result in your favour if you ask a negative question like that.
You should avoid that in the future, this poll here doesn't give any usable information, neither for you nor for Riot.