[quote=GoodSamaritan]How would you answer the accusation that things such as the rosary, Ash Wednesday, Lent, abstinence from meat on Friday, and Chaplet of Divine Mercy are merely traditions of men?
By agreeing that they are manmade traditions. Then I would ask “Does the fact that they are manmade mean that they are therefore bad traditions?” If the person said yes, I would ask if he celebrates Christmas, Thanksgiving, his birthday; if he or his wife wears a wedding ring, takes flowers to the cemetery, says mealtime grace; if his church has altar calls, worships on Sundays, has stained glass windows. If he or his church does any of these, he is participating in manmade traditions that should be repudiated if he is to be consistent with the principle with which he professes agreement.
[quote=GoodSamaritan] … and not things that Scripture remotely implied?
We can quibble over what Scripture “remotely implie[s]” because no two people are going to agree on all of the remote implications of Scripture. It is one of the reasons sola scriptura is a faulty doctrine. For more information on the place of tradition in the Christian religion I recommend Scripture and Tradition. But, as one example that the person is incorrect that the customs you mention are not supported – at least in principle – by Scripture, let’s look at Lent.
Lent is a forty-day period of penance and preparation for Easter. In the Bible, forty days often signify such periods of purification (cf. Exod. 24:18, 34:28; 1 Kgs. 19:8; Jon. 3:4-8; Matt. 4:2). If one could set aside a time of fasting and penance in preparation during biblical times, why we may ask is it considered unbiblical to do so today?
[quote=GoodSamaritan]What is the purpose of these things?
The ultimate purpose is to open us to God’s grace and through that grace be brought closer to him. In short, the purpose is to strive toward sanctity (cf. 2 Tim. 4:7-8).