This post should have been written during TAFTO month, but I am quite late. Nevertheless, I have things to say, and promised to say them. One reason why lay people are resistant to attending classical concerts is from fear of appearing uncultured. What can be criticized, what must be worshipped, what is horrendous to admire? Classical music fans and practitioners can be snobbish, expressing horror when someone expresses a dislike for Beethoven's Emperor Concerto or Mozart's Sinfonia Concertante. I myself have felt knee-jerk reactions when people tell me they hate a particular contemporary work. I have been working on respecting these people's opinions, and in engaging in a dialogue about the music rather than a lecture.
I think it is okay to challenge the opinions of neophytes, but said challenges should not be based on the weight of authority, and always with the philosophy of chacun à son goût. If your friend doesn't like Beethoven's piano concerto, ask why. It may be too long, too much of the same, no lyrics, etc. Address any of those concerns with your own feelings and with suggested listening strategies that could counteract those negative vibes. But also accept that the person may never like Beethoven, and is not a lesser person for feeling that way. I can respect someone who feels strongly in opposition to me, as long as that person is open to hearing my opinions and can express their own opinions respectfully and cogently.
Neophytes usually do not know the technical language of music, but that does not prevent a full discussion. Terms can be defined, descriptions can be clarified. And that comes around to my own opinion on how to increase audiences at classical concerts: two-sided conversations and non-dogmatic attitudes.