I was traveling on a CO mainline from Houston to Laguardia in a 738. When I reached my seat there were two people both trying to take one seat just behind me. An older gent and a laidy that had to be 8 months pregnant. I offered the laidy my seat but they were both hell bent on the assigned seat. After five more minutes the gate agent came down and told the guy to take the last first class seat. The man looked at me and then at the laidy then asked me if she could take his seat in first. I told him I did not see a problem with it at thanked him for his generosity. Long story short, this ****ed off the FA's so bad that I got sent to the perverbial principals office and then they proceded to verbaly abused me the whole flight. One guy actualy took the drink cart and ran it straight into my leg while I was passed out. The messed up thing was he backed up and did it agin. It left a nice bruse. I learned real quick that people look to you when your in uniform to resolve there issues when it is not your place. And also those main line FA are a pain in the but.