There are some healthy cautions in here, against "over-doing" the guarding-your-heart mentality. But there is a lot to filter out as unhelpful, too.
I've read two of the three books pictured at the top of the article. I assume they are meant to represent the beliefs critiqued by the article. I can understand criticisms of people like Lindvall and Doug Wilson or Josh Harris for their views of how dating should go. But Elisabeth Eliot? Wow.
Children who grow up in overly strict homes usually have an adjustment to make. They will tend to over-adjust by over-emphasizing (distorting, really) grace and under-emphasizing a healthy fear of falling into real sin. Can grace really be over-emphasized? Not the true version. But it can be distorted, yes. See Romans 6:1 for an example.
To say that guarding your heart is based on fear is a half truth. Is the fear well founded or over-protective? I don't leave my ipad in precarious positions high over hard floors, just to have the experience of losing something valuable, or just to avoid living in fear. How much less am I careful who I give my heart to? Neither do I have to put the ipad in a glass case and never open it to anyone.
It is true an overly scrupulous application of this can lead to false guilt. Stollar calls it shame. You feel guilty but haven't actually sinned. If you start to like a guy, you haven't sinned. It's what you do with that feeling that you are responsible for. Does a person always have a piece of your heart, even if you break up and marry someone else? That might be a little strong, but regrets do linger over romantic relationships before your marriage. These need not be sinful, but it's always with you, and why not avoid regrets? It's true that God redeems such experiences. He is gracious and merciful. But we don't go sin or act recklessly, that grace may abound, either.
Emotional purity teaching can cause pride? Yes, it can. But that's not an argument for or against the teaching. Teaching any moral standard can cause pride, whether the standard is biblical, or extra-biblical. The problem is the heart that exalts itself. Bragging about not kissing (silly) or not saying I love you (disturbing) before the wedding does show a heart of pride. Neither is required by the Bible. But refraining from kissing before the wedding day does not make you a legalist or proud, either.
Emotional purity teaching makes you feel guilty for having a cross-gender friendship? Almost every guy-girl relationship especially among young people is sexually charged, so to speak. People should tread carefully here. I think of Billy Graham who made it a policy never to be alone in the same room with a woman. This is just a healthy precaution, not a proud and fearful Pharisee at work. Of course, if your friend's spouse steps out of the room momentarily you don't have to freak out. But a conscience sensitive to being in vulnerable situations is better than being oblivious to potential trouble. This isn't a legalism versus grace issue. We don't need to recreate a Victorian culture where men only talk to men and women only to women. But social interactions should take into account that men and women are different, and not interchangeable as modern life tries to tell us.
Emotional purity over-emphasizes safety with formulas? Yes, it can. I've seen this attitude quite a bit. If I just stay in God's ways I won't get hurt. Putting this in absolute terms is a problem, but I think Proverbs does affirm anecdotally that obedience leads to life and disobedience to destruction. Externalizing purity with outward rules alone is a problem. But a heart of purity will lead to refraining from certain outward behavior.
One thing I learned from this article, especially at the end, is that if we haven't persuaded our children from God's Word of the rightness of how we raise them, the fruit won't get far. The older our children get, the less we should impose extra-biblical, house-rule standards on them that they won't accept. For clear Scriptural principles parents can and should say, "As long as you live in my house you won't do x, y or z." But if a teen won't accept your guidance, then parent-guided relationships aren't going to work and shouldn't be forced, no matter how much dad has bought into courtship.
Stollar calls the fruit of this movement rotten. I would argue that that bad fruit comes from (truly damaging) over-zealous and -strict application of truly helpful Scriptural principles.
PS - I don't endorse this website, but it can be helpful in self-evaluation for homeschooling parents.