Cynical people all day

Recently, I hung out with a friend who repeatedly made disparaging comments about long term relationships, marriage and all. She is convinced that people in long term relationships are stupid and are not really happy. Well of course conveniently ignoring or maybe trying to take a slight jab at me since I am in a long term relationship. I just simply said that all people are different. Some people can be happy in long term relationships, some aren’t.  She wasn’t too convinced and continued to make cynical remarks, despite the fact (puzzlingly enough) his parents have been happily married for about 30 years, which she admits they seem pretty happy. A lot of people who are staunchly against long term relationships or marriage are either a.) hurt too much by past experiences (but I’ve found many of those people can be rehabilitated) or b.) they’ve never been in an actual long term relationship or had any real experience with romance. Maybe she watch lots of people break up and get hurt so she start to get this smugness “Ha! I’ve never been hurt and I’m better for it!" She told me that she heard about people making mistakes and falling in and out of love and they say “HA! YOU FOOLS!” As if they know better. As if their lack of experience simply makes them “smarter.”  As if they “chose” to not be in a relationship because they are so “smart.” But how can they even know or understand if they’ve never even been in those people’s shoes? Honestly, if you do not have experience, why dole out advice on something you really know nothing at all aboutWhenever I hear about people having issues with their relationships, I don’t rush to judgment, because while I have relationship experience it doesn’t mean I necessarily understand EVERY issue in relationships. All relationships are dynamic because every person involved is different. Sure they can be some guidelines on what is a successful relationship but it’s not the end all be all; different things work for different people. So as you can tell, my friend falls under the “b” category. She’s never had a relationship. She becomes more self-conscious of her “lack of experience” and in response she has the following defense mechanism

    “Obviously I’ve never been in a relationship because I CHOOSE not to, because relationships are dumb and only stupid people do it. And it’s a waste of time that prevents you from being successful and satisfied in life. After all it just leads to break-ups and what not etc…” Which is silly because she knows plenty of people who are in relationships and successful and happy.  Perhaps she wants to convince herself they really aren’t?

Ultimately, I think the smart thing to do is if you do not have much experience in romance or relationships you should give advice in a limited capacity.  Just like I wouldn’t ever try to dictate an opinion to a surgeon regarding some complicated surgery she is about to perform, simply because I have watched live surgeries and looked up procedures online. That would be dumb. 
I guess I’m just frustrated with some cynical people like her. But do you agree? Shouldn’t people gauge their knowledge base and then respond accordingly? Or are you just like my friend, who thinks she knows everything despite lack of experience?   
Well but I do believe someone with no direct experience maybe able to give a different point of view from the outside in, I wouldn't rule that advice out.  However, it's tough to be around cynical people all day, that's probably the biggest issue here.