It has become very common over the internet that whenever a "Catholic" does not agree with the Pope or teaching of our current bishops in communion with the Pope, they take the sources of old Saints (and in many cases they misinterpret them) in order to support their idea.
Here is an example, a website where its author apparently agrees with alleged opinions of some Saints in order to promote schism with our current Pope and Magisterial teaching on the matter:
Even if the alleged opinions of those Saints are true, their personal opinions are not over Magisterial Teaching. A person cannot be at the peak of holiness all the time, a person may be less holy at times, or not holy at all at other times. Also, a person may be very holy and yet ignorant on a subject matter because the fact that a person is ignorant about something, does not mean that he is sinful. And a person can be very holy and yet fallible for we are all fallen creatures.
The Magisterium is here to teach and correct us. Before the Church teaches on a subject matter, we can have our opinions on open questions, but once the Magisterium has spoken a teaching, case closed.
That site says nothing about the experience that St. Francis of Assisi had with the Moslem.
St. Francis walked across Muslim lines unarmed in order to meet Sultan Malik al-Kamil of Egypt for a peaceful dialogue. Did the Sultan beheaded Francis for being an ‘infidel’? No, a good relationship began to rise between them. St. Francis never told the Sultan that he was going to convert to Islam, no; he kept his Catholic Faith all the way during and after the peaceful conversations with the Sultan so that the Franciscans (yes, non Muslim believers) were granted permission to get in and out those grounds taken by the Muslim whenever they please. Sultan Malik al-Kamil of Egypt was a true follower of his faith.
I also have personal experiences with followers of Islam at a previous job and now in my current job.
They interact with me in a friendly manner, they don't hide that they are Moslem and I don't hide that I'm Catholic, we joke around, have fun, dialogue, I notice that women in particular are very humble, and I'm not making this up. This is my real experience with them.
So what the Popes and the Magisterium teaches us in the matter must be true! I believe them.
If I'm incorrect on something I have said here, or if I'm missing something, please don't hesitate to let me know.