Dr. Dominic Bagnoli has sometimes been dubbed a visionary for growing a three-physician emergency medical practice into a Canton-area powerhouse that now manages ERs at 170 sites across the country.Yet when Bagnoli’s company went to work in his own backyard Jan. 1 — abruptly taking over Summa Health System ERs after last-minute contract negotiations fell through with Summa’s longtime provider — Bagnoli said he was unfairly depicted as a villain.“We stepped up to see patients at financial risk and we’re the bad guys?” Bagnoli asked during an interview last week.