Here, "I mean" is used to introduce a following clause which modifies the prior one. This usually has the effect of altering a very strong and general statement to instead reflect a specific contention.
2. "What's your favorite movie?"
"Hmm... I mean... I like Mission Impossible, but I also love Die Hard."
Here "I mean" covers the speaker's thought process and indicates that conflicting ideas are being weighed in the speaker's mind. It indicates that an answer has not yet been formulated, but does not invite the other speaker to continue talking.
3. "Man, that song is really great!"
"I mean, if you hate music."
Here "I mean" is used to indicate that the speaker has briefly thought of a more polite way to indicate the statement but can only express it in a blunt or sarcastic fashion. "I mean" only starts a statement of this nature if it is in response to someone else's statement, though it can be used in both to agree and disagree with said statement.
“I mean…like…one day…like…I will be the most successful…like…lawyer or teacher…like…I mean….just like in that movie…like…I better buy some pink clothes...i mean”
See also: I know, right?, seriously
Arthur: I mean, they look like they've never played before!
Randy: I could really go for some Fuji Chen right now.
Derrick: Oh god. I mean, some Sesame Chicken would really hit the spot right now. Mmm.