Should everyone get a second opinion for a diagnosis of non-hodgkin lymphoma?

Yes. But there are conditions. If you trust your doctor and you are comfortable with him/her and may be necessary to start treatment while you seek a second opinion. If you have an aggressive lymphoma or one which is causing a serious problem: ie organ failure, you might not have the time to seek a second opinion before you start therapy. You can still get the 2nd opinion however after you start .
No. Getting a 2nd opinion is always reasonable. However, "should everyone get a second opinion..."? No. Nhl is a common diagnosis that most heme/onc's are highly familiar with. If you have any concerns about your doctor or facility you may want a second opinion. If you have an unusual cancer or difficult to treat disease than potentially.