Not at all. There are other races with only left turns, and NASCAR has some races with right-hand turns as well.
Muggle quidditch is the only sport played with a broom between your legs. 
(It counts, I’m pretty sure the broom is incidental to gameplay.)
Okay, I’ll bite–why is this? Because you grab the opponent’s clothing to throw them and stuff?
(My ignorance of judo is limitless.)
Yes. There was an interesting international once when the ground rules allowed for extensive repairs before each day’s play. After initially being outplayed, England had to make the immense score of 696 to win in a match with no time limit. (No international side has successfully chased anywhere within 200 of this.) Presented with effectively a new pitch every day, England applied themselves heroically and got past 650 with batsmen to spare. Then rain, and the need to catch the train to get to the port for their ship back to England, brought the no-time-limit game to an end. Scorecard.
I don’t know if it’s unique to baseball, but certainly unusual is that every field can have different dimensions.
I’m having a hard time parsing this exactly, but would curling qualify? There, the players themselves actively change the surface as a part of play, and the officials deliberately render the surface non-ideal at the start.
All the holds and throws utilize clothing, if the opponent is not wearing clothes, many of them cannot be done.
Sumo is the only sport where a particular hairstyle (not length/shortness requirements, but an actual hairstyle) is part of the official uniform.
Not really.
Every soccer pitch can have different dimensions for non-international matches i.e. 91–120 m length and 45–91 m in width, provided that the pitch does not become square though internationals are played on a standard sized field.
In Australian Rules football every ground has different dimensions in a range of 135-185m long and 110-155m wide. The same applies with cricket, hurling and gaelic football.
Actually, that does fit in a somewhat similar way, and really, it is more active in curling than in bowling. Pardon my ignorance – I actually like watching curling, but in what way do the officials make the surface non-ideal?
If you were saying that you didn’t understand my statement, I’ll explain briefly. In professional bowling, patterns of oil are put on the surface of the lane such that certain parts of the lane are dryer, and some are oily-er (causing a rotating bowling ball traveling over those portions of the lane to hook more or slide more, respectively). As a bowling ball continually hits a given spot on the lane, it either absorbs or pushes the oil around. This means that, after practice, a professional bowler may find that having his ball cross the arrows at the 10th board may be ideal for his shot. But by the fourth frame, conditions will have changed enough that he will have to move his feet or where he is aiming in order to hit the pins the same way. Those adjustments will increase in number and severity as the contest goes on. Most profesionals are able to hit a given spot consistently, but a big part of the game for them is being able to anticipate the changes they need to make for each shot.
Yes. The standard judo stance/grab is one hand holding the opponent’s sleeve at the wrist or elbow, the other hand holding his collar next to or behind the neck (which is why judo kimono have such thick, reinforced collars and seams). Many holds and throws apply leverage to the kimono itself rather than the man wearing it, and can fail hilariously if the opponent’s belt is not quite tight enough. There are also belt grabs and throws.
Of course, holding the wrist itself rather than the sleeve, and throwing a headlock rather than using the collar is possible if you need to throw a guy around in a real fight - it’s just Not Done in formal judo, and many throws and holds cannot be used without an opponent wearing a proper kimono either (e.g. there are lots of ways to choke a guy with his own reinforced kimono collar - good luck choking a guy with his T-shirt 
)
Uh, well, yeah. Just like you can’t use your hands in soccer, but you toss the ball in when it is out of bounds.
Once the ball is in play, you can’t touch it with your body.
Were you kidding?
Every golf course is different. And in the major tournaments, the course itself is different every day. Different hole positions, and different tees.
Isn’t hockey like this a bit?
Is (American) football the only professional sport where play will continue in any weather unless it represents a deadly threat to anyone in the area?
I think I learned this from a thread here, so if someone else knows better, feel free to correct me. But it’s my understanding that after the ice is smoothed, an official will throw a bunch of droplets into the air to freeze into little lumps on the ice.
penultima thule, am I reading that correctly that you could fit two or more complete small soccer pitches onto a single large one? I wouldn’t have guessed it’d be that extreme.
AFAIK korfball is the only sport where teams must be composed of men and women. Of course other sports may have mixed teams, but only korfball requires it.
I believe rugby is the only solely outdoor sport which has immovable foreign objects completely within the field of play and in which a ball can touch said objects and still be in play. Canadian football still has its goalposts on the field of play, but if a ball touches them either by being kicked or thrown the play is whistled dead.
There are a few ball-and-wall sports with only three walls, but only jai-alai has one long wall and two short ones.
Golf is the only sport in which spectators are permitted to bring players’ rule infringements to the attention of the officials. (Although it would make other sports more fun.)
Cricket is the only ball sport where players may legally tamper with the ball (within strict limits, however).
Do the posts of a hockey net not count?
I recall reading that boxing was the only sport in which the score is unknown to the participants, the referee, and the spectators until the contest is over.
Lacrosse goals, too.
Professional bicycling-the team works together to give the team leader an individual victory.
Aren’t baseball, softball, and cricket unique in that in each it’s the defensive side that controls the ball?