The Protestant notion of "faith alone" has always been a little strange to me, even when I was a protestant. It didn't seem to take into account the way that God's grace transforms us to be more like Him.
Can someone who has faith, but doesn't love, be saved?
The answer is obviously no.
To say otherwise is to invert Paul's hierarchy of virtues: "And now these three remain: faith, hope and love. But the greatest of these is love." 1 Corinthians 13:13
We know that love is necessary. But a good protestant might object that the sort of faith we're talking about isn't simple belief, but a "loving faith." That's fair enough.
But then the challenge is why use the phrase "faith alone" when we really mean "faith + love?" In fact, the phrase is even more suspicious than that. Consider that this is the only time the phrase "faith alone" appears in scripture…
"You see that a person is justified by what he does and not by faith alone." James 2:24
Here is what the Catechism says about Faith…
1814 Faith is the theological virtue by which we believe in God and believe all that he has said and revealed to us, and that Holy Church proposes for our belief, because he is truth itself. By faith "man freely commits his entire self to God."78 For this reason the believer seeks to know and do God's will. "The righteous shall live by faith." Living faith "work[s] through charity."79
1815 The gift of faith remains in one who has not sinned against it.80 But "faith apart from works is dead":81 when it is deprived of hope and love, faith does not fully unite the believer to Christ and does not make him a living member of his Body.
1816 The disciple of Christ must not only keep the faith and live on it, but also profess it, confidently bear witness to it, and spread it: "All however must be prepared to confess Christ before men and to follow him along the way of the Cross, amidst the persecutions which the Church never lacks."82 Service of and witness to the faith are necessary for salvation: "So every one who acknowledges me before men, I also will acknowledge before my Father who is in heaven; but whoever denies me before men, I also will deny before my Father who is in heaven."83
79 Rom 1:17; Gal 5:6.
80 Cf. Council of Trent (1547): DS 1545.
81 Jas 2:26.
82 LG 42; cf. DH 14.
83 Mt 10:32-33.