Swarthmore is not a less liberal LAC. Rather, it is one of the most liberal LACs out there.
Although my kids didn’t report this, we know some other students who felt turned off by what they perceived as more of a monolithic, homogeneity of viewpoint on campus, similar to what the OP described. Those students were perfectly comfortable at other left-leaning schools.
Yes, Centre is quite politically balanced. I did a visit this month and asked my tour guides about this specifically. Very nice facilities there.
Bucknell, Lehigh, Franklin and Marshall, Dickinson and Gettysburg all might be worth investigating.
Vassar, Bard, and Swat are NOT what this student is looking for. Lots of other good suggestions, though.
What I took from OP’s question was that, she self-describes as “progressive and quirky” but thought Oberlin might be a community which did not handle difference of opinion well. Many other LACs would fit that niche, including Kenyon, Dickinson, Denison, Conn Coll, Skidmore, Macalester, Grinnell, Wooster, Earlham, Kalamazoo etc.
@tonroxmysox and @intparent - yes, Bard/Vassar/Swat are left-leaning but I was under the impression that Oberlin was even more so. Hence the “maybe” for those three from an OP who describes herself as a quirky progressive. Did not mean to mislead.
Swat is very, very far left. We are liberal (I used to sit on our state Dem party committee), and D2 and I both honestly found Swat off the deep end liberal when D2 went for her accepted student visit. More so than even Oberlin.
I am sure this is the very first time I’ve heard someone say that. I’d have thought Oberlin was “out-liberaled” only by Antioch (and I speak as someone with a close family member Antioch grad, an almost-Oberlin attendee me and my D, and a Friends HS grad, which Swat is, of course).
What was it that was so left-ish for you?
@intparent - interesting to know! I don’t have personal experience with Swarthmore except for a family friend who taught in the English department, long since retired, a stately elegant woman who wore twin sets and pearls. Everything else I’ve gleaned from the internet. I must dig deeper, I guess. Thanks for offering your personal perspective.
We missed Swarthmore on our last college tour, not enough time. We did visit Vassar and didn’t find it too “out there.”
Trinity, Holy Cross, Colgate, Bucknell. Of the top LACs, Williams has a rep as being a bit more athletic/well-rounded than super left leaning. Probably Middlebury and Bowdoin too, and maybe Colby and Hamilton.
It seemed like every presentation and every student was trying to “out social justice” each other. “I gave up my med school aspirations to start a dance non-profit in the Ninth Ward post-Katrina!” “I was going to major in Econ, but decided to go to India to found a non-profit to improve the education system there.” (Student does not appear to be Indian) These were real student presentations that were part of the parent accepted student activities. Add a recent takeover of a Swat board meeting by protesting students.
We are UUs, and no strangers to social justice or non-profits or community service. But this environment of high performing students felt like it was just straining to out do each other on this front. It was so intense… my kid said the morning after accepted student overnights that if she heard the phrase “social justice” one more time she would throw up. She really thought Swat might be “the one” before that visit, but said she thought it was too impractical and hyper focused on that topic. My cousins attended there years ago, and adore it. But not sure it is the same…
Certainly Oberlin is crunchy and liberal, and they recycle poop in the basement of one of the buildings, which we found rather cool. 
Oberlin has overly PC moments, and is proudly progressive. But it was sort of the essence of Oberlin… we felt bludgeoned by it at Swat.
Holy Cross, Bucknell, Colgate.
Engineering students and professors are typically more conservative when in a liberal arts school’s setting. even if you won’t go into engineering, it helps to look for LACs with a strong engineering program for this vibe. My dad went to Lafayette and the political balance was a very important thing to him, so he loved having more liberal English Major friends and more conservative Engineering friends.
What we found at Swarthmore were incredibly intense (and tense) students who took things a bit far. They seemed competitive (?) even in their activities and community service. It was a weird vibe. That was what turned my child off. They couldn’t let loose and just be.
Every few years, a catch phrase takes hills and everyone uses it as much as they can. Twenty years ago, it was “sustainable development” and “social movement”. Now “social justice” has taken hold - at least at Swarthmore. I can see how the intensity of students and focus on the latest cause can turn someone away. I don’t think it’s so much that Swarthmore is ultra liberal in the social or political sense, it’s more their intense and earnest personality.
Go back and check out some of the stronger Division III colleges, starting with NESCAC and the Patriot League. How well attended are the sporting events? How well do they support traditional spectator sports like football, basketball and baseball? I think you’ll find a correlation between school spirit and a “moderate middle”, politically speaking, at any given college.
For school spirit at LAC’s, Holy Cross, Davidson, and Bucknell are tops.
Have you considered Kenyon? IMO, has a more moderate feel than Oberlin, while still being open and welcoming.
If you’re still looking, consider Denison. It’s liberal overall, but is one of the more moderate liberal arts colleges I’ve been to. Kenyon is more liberal than Denison but more moderate than Oberlin.