I attended last night @ Fenway and am a reasonably travelled baseball fan having gone to ALL active MLB parks, plus some in Japan, etc.
Let me admit my heritage as a Midwest guy tainted by several decades in the Northeast. What I like about baseball is it is outside and as a Minnesota child my Dad took me to see the Twins (Twinks) in their 1965 World Series vs LAD.
Typically baseball STILL is a great family outing. Sit in the sun, chat with fellow fans, buy the kiddies a hot dog and enjoy universal sights & sounds of baseball - hawking vendors, the smell of hot dogs, colorful people, peanuts and a late-inning rendition of Neil Diamond. Almost always you're welcomed as a guest when locals learn you're an out-of-towner. They are proud of their team, their ballpark and are eager to help you find the best restaurant and things to do during your stay. No animosity if you clap for the visiting team.
So anywhere from San Diego to Toronto, Milwaukee to Tampa Bay, even Anaheim baseball fans are great folks and attending a game as a visitor is family friendly and safe. No thrown beer, no jeers, no "Yankees suck" catcalls or insults per the visiting team's cap you're wearing. PLUS - you can afford to park and buy the family a hot dog and soda without a 2nd mortgage.
But like most rules there are exceptions and in my experience there are 4 definite and 1 maybe exceptions where friendliness is not the rule: New York Yankees, New York Mets, Philadelphia, BOSTON - and arguably Chicago White Sox. I've been to all including Playoff games at Yankees, Mets, and 30+ at Fenway. Civility is not the norm.
Fenway is better than in the 90s & early 2000s where NYY/RS matchups needed heavy police presence. Drunkenness is down and last night was reasonably cordial with no fights near me. Pedro vs Don Zimmer altercations are less common.
But I'm a fan and these are my area teams, so I go. For those who been jaundiced by the ridiculous salaries, off-field antics, entitled attitudes or questionable safety of the Yankees/Red Sox in particular - you have cause. However I do think baseball is a better kid attendance sport than the other majors and I would encourage even the doubters to let their kids experience what can be a lifetime memory for the positive.