Swearing shows somebody is angry at something, and that's definitely unchristian..:)
"Do not make friends with a hot-tempered man, do not associate with one easily angered" (Proverbs 22:24)
I like this text with what you stated:
Eph_4:26 Be ye angry, and sin not: let not the sun go down upon your wrath:
So there is a proper and right anger that should not cross into sin.
Mat_5:22 But I say unto you, That whosoever is angry with his brother without a cause shall be in danger of the judgment: and whosoever shall say to his brother, Raca, shall be in danger of the council: but whosoever shall say, Thou fool, shall be in danger of hell fire.
Jesus was angry, and sinned not:
Joh 2:13 And the Jews' passover was at hand, and Jesus went up to Jerusalem,
Joh 2:14 And found in the temple those that sold oxen and sheep and doves, and the changers of money sitting:
Joh 2:15 And when he had made a scourge of small cords, he drove them all out of the temple, and the sheep, and the oxen; and poured out the changers' money, and overthrew the tables;
Joh 2:16 And said unto them that sold doves, Take these things hence; make not my Father's house an house of merchandise.
Joh 2:17 And his disciples remembered that it was written, The zeal of thine house hath eaten me up.
Mar_3:5 And when he had looked round about on them with anger, being grieved for the hardness of their hearts, he saith unto the man,
Eph_4:31 Let all bitterness, and wrath, and anger, and clamour, and evil speaking, be put away from you, with all malice:
Col_3:8 But now ye also put off all these; anger, wrath, malice, blasphemy, filthy communication out of your mouth.