9 But avoid foolish questions, and genealogies, and contentions, and strivings about the law; for they are unprofitable and vain.
Paul warned Titus, as he warned Timothy, not to get involved in arguments over unanswerable questions (2 Timothy 2:14). This does not mean we should refuse to study, discuss, and examine different interpretations of difficult Bible passages. Paul is warning against petty quarrels, not honest discussions that leads to wisdom. When foolish arguments develop, it is best to turn the discussion back rack that is going somewhere or politely excuse yourself.
10 A man that is an heretic after the first and second admonition reject;
11 Knowing that he that is such is subverted, and sinneth, being condemned of himself.
*a heretic - divisive, subverted - warped
A person must be warned when he or she is causing division that threatens the unity of the church. This warning should not be a heavy-handed action, but should correct the individuals divisive nature and restore him or her to fellowship. A person who refuses to be corrected should be put outside the fellowship. As Paul said, he is "condemned of himself" - he is sinning and he knows it.
(See also Matthew 18:15-18 and 2 Thessalonians 3:14,15 for help in handling such problems in the church.)