It doesn’t look like this tool is very sophisticated. It appears to have looked for words that are similar to each word you entered, as well as the entire phrase that you entered. So there are words that match:
Offering: take, pass, give, make, voluntary, volunteer
Ones/own: personally, private, conscience, autograph, self-interest, egoism
Opinion: think, opine, counsel
Since any word that is returned by searching “opinion” will probably also be returned by “offering one’s own opinion”, it’s hard to tell which might be the result of the algorithm trying to match the entire phrase. Some of the words in the list are characteristic of offering a negative or unwanted opinion (chauvinism, intolerant, etc.), but they still sort of fit your search terms.
But there are also, as you say, a lot of words that don’t fit any of these terms individually or as a phrase. I can only think that this happens because other people who entered some of your words in the past also entered terms that matched these.
Basically, the search engine seems to be trying to think too hard. But I’m just offering my own opinion. ;)