Should one openly condemn widespread transgressions in public places, such as immodest display (tabarruj) and shaving the beard, or not?

You must always condemn evil in your heart. Condemning it with your hand and tongue is contingent on your ability to do so and the safety from harm. If you are unable to condemn it, or if doing so would result in harm, then it is not obligatory for you. It is not necessary to deliver a lecture; rather, it is sufficient to address the one committing the evil with gentleness and kindness, explaining the error to him. Ignore feelings of weakness, and continue your normal life, enjoining good and forbidding evil to the best of your ability. Repent and seek forgiveness if you fall short.