In simple terms, the phrase "same banner" means being part of or supporting the same group, cause, or team.
Sentences with «same banner»
This effort often goes under the same banner of inclusiveness that justifies the church's outreach to members of different races, classes and ethnic backgrounds. (religion-online.org)
Yeah, Paul may have given the theology that later writers tried to put meat and bones on — with all their stories, then can the multitude of spin offs — all of them using the same banner but each carrying their own agendas. (nakedpastor.com)
You took an obscure (to me) host who said some off the wall things and used it to castigate conservative talk show hosts under the same banner — I paraphrase the quote» conservative talk show host spewing their hatred...» Or some such phrase. (redeeminggod.com)