I don't blame them. If they lose a Congresssional seat now they probably won't ever get it back. On the other hand Stenholm has a pretty conservative voting record. The only thing he doesn't do is vote for the Repblicans to organize Congress. Whenever Stenholm decides to retire, his district will probably elect a Republican. Considering he only received 51% of the vote when he ran for reelection in 2002, that retirement might not be voluntary.
Read your Constitution. Redistricting occurs after every decadal census. It's meant to ensure that the House of Representatives remains that, representative. Current law is a little vague (to me) as to the maximum citizens in a US House district, but the minimum remains at about 160,000 citizens. Maximum number may be [current national population] divided by 435.