It has been my experience that most of those who go door to door, stand on the street corner, or confront people in public teach heresy.
Interesting comment. My husband and I have a friend, and he button holes people every time he walks down the street. He also has a very thick accent, so my thought is that people don't understand him, even if he was just asking for directions.
He has been doing this for the 34 years we have known him. And he does love to do it in front of other Christians as he has certainly done it in front of us, often enough.
The results? No one has ever gotten saved, or even asked for more information, to go for coffee to talk about it. Not in all that time. But he does look good to himself and other Christians. I know I was certainly fooled by his act for years. My husband still is!
Something about "being rewarded in secret?"
Regarding the heresy - this man, and I do love and care for him as a brother in Christ, has possibly the worst theology I have ever encountered. Forget about Jesus not being God, there are millions of others who could be Christ but are not God. (Or something?) He knows his Bible, he just doesn't understand it. He doesn't get how to interpret and understand. When he is in a church like United Pentecostals,he believes what they do. If it is Word Faith, then he is personally being used by God to heal people. (Except he goes to the doctor as quick as a wink, when he is sick.)
He seems to be in a balanced church right now.So he is pleasant to discuss the Bible. But should he leave...
Anyway, I have never heard of anyone getting saved by a random person just picking them out and witnessing to them. Although of course, God can use anyone in any place.
I just think we need to develop relationships and meet people where they are at. And also not be afraid to speak a word in season about God, when the Holy Spirit prompts. And not to worry about the resullts. That is for the Holy Spirit to take care of. We do need to be on mission with God, all the time. I agree with the OP.
Being on mission means following what the Holy Spirit is telling us to do and trusting him for the results.