At the time, pundits hostile to Paul quickly victim-blamed for the vicious assault, which gave Paul six broken ribs and lung lacerations. GQ declared him an "asshole neighbor" who is one of those troublesome "Libertarians [who] don't want to follow the rules that we as a society have agreed upon, because they feel those rules step on their freedoms." (Apparently, someone accused Paul of "believ[ing] in stronger property rights than exist in America" because he composts and grows pumpkins on his property.) The New Yorker similarly praised attacker (and Democrat!) Boucher as a "near-perfect neighbor" and looked suspiciously on the libertarian-leaning Paul for thinking all that property rights stuff maybe meant he shouldn't be sent to the hospital by his "near perfect neighbor" for things he did with his lawn.
Politico saw Paul's inability to come to a Coasean solution, irrespective of property rights, of whatever grievance prompted his neighbor to break his ribs as a sign that "one or both of them is a jerk. I believe that this is an excellent working hypothesis. I've seen Senator Paul up close. He is, let us say, pretty high on himself." USA Today gave the developer of the two men's housing association space to condemn Paul, without much in the way of actionable specifics, for wanting to control his own property too much.
Now the specifics of what motivated Boucher—unknown, it should be stressed, by all the above pundits and reporters who were sure it was Paul's fault—are more well-established in the public record as Boucher seeks probation instead of jail time for his crime.
Boucher was very upset, apparently, by piles of brush on Paul's property, though within sight of Boucher's. He had been reacting to these offending brush piles by paying to have them hauled to dumpsters, then by setting a yard fire to destroy them (so carelessly that he gave himself second-degree burns), and eventually by attacking Paul.
In addition to the brush piles in his neighbor's property, Boucher also insists that Paul's use of a lawnmower the day of the attack blew some leaves onto Boucher's property—the only activity of Paul's that sounds even close to a legitimate complaint, though obviously not a "send neighbor to hospital" level of complaint. Sometimes, even a person with libertarian leanings doesn't deserve to have six of his ribs broken for believing he has some rights to use his own property.
UPDATE: Sen. Paul's office provided this statement about Boucher and his claims:
Before Senator Paul was violently attacked from behind, he had no conversations or discussions with the attacker. There was no "longstanding dispute." This description is untrue. It is impossible to have a dispute when no words of disagreement were ever spoken--neither immediately nor at any other time before the attack occurred. In the decade prior to the attack, Senator Paul had no contact with the attacker. The attack was a pre-meditated assault that broke six of the Senator's ribs and was complicated by fluid and blood around the lung and recurrent pneumonia. Any description of this attack that implies a "yard dispute" justifies such violence misses the point.
Correction: An earlier version of the post and its sub-headline stated that Paul had only five ribs broken.