Controlling the Curse
I'm not certain about 5e, but at least in 3.5 a character has the ability to controll their Lycanthropy. I found the following information about afflicted Lycanthropes (those that contracted the curse/disease by being bit by a natural Lycanthrope):
When a character contracts lycanthropy through a lycanthrope’s bite (see above), no symptoms appear until the first night of the next full moon. On that night, the afflicted character involuntarily assumes animal form and forgets his or her own identity, temporarily becoming an NPC. The character remains in animal form, assuming the appropriate alignment, until the next dawn.
The character’s actions during this first episode are dictated by the alignment of its animal form. The character remembers nothing about the entire episode (or subsequent episodes) unless he succeeds on a DC 15 Wisdom check, in which case he becomes aware of his lycanthropic condition.
Thereafter, the character is subject to involuntary transformation under the full moon and whenever damaged in combat. He or she feels an overwhelming rage building up and must succeed on a Control Shape check (see below) to resist changing into animal form. Any player character not yet aware of his or her lycanthropic condition temporarily becomes an NPC during an involuntary change, and acts according to the alignment of his or her animal form.
A character with awareness of his condition retains his identity and does not lose control of his actions if he changes. However, each time he changes to his animal form, he must make a Will save (DC 15 + number of times he has been in animal form) or permanently assume the alignment of his animal form in all shapes.
Once a character becomes aware of his affliction, he can now voluntarily attempt to change to animal or hybrid form, using the appropriate Control Shape check DC. An attempt is a standard action and can be made each round. Any voluntary change to animal or hybrid form immediately and permanently changes the character’s alignment to that of the appropriate lycanthrope.
I found the following about the 'controll shape' ability:
If you have contracted lycanthropy and are aware of your condition, you can learn Control Shape as a class skill. (If you are an afflicted lycanthrope not yet aware of your condition, you can attempt Control Shape checks untrained.) This skill determines whether you can control your shape. If you are a natural lycanthrope, you do not need this skill, since you have full control over your shape.
How would characters react?
Lycanthropy has quite some obvious pro's and cons, but in the end the reaction of the character would depend on the character in question. Lycanthropy can make a character quite powerful, but it obviously comes with a certain 'loss of self'. Even if a character manages to controll his/her curse, they may eventually change their entire allignment due to the effects. I would assume that most characters who know the full details of lycanthropy, or those that are superstitious and fearful/hateful of all things normally seen as dark and evil, would loathe their curse and wish to be rid of it. A few pragmatists may see the benefit in the curse, if they are able to controll it. It comes with some pretty nice stat bonuses, and the Hybrid form combines the best of the animal form and humanoid form.
Changing in every way
A Lycanthrope doesn't just change in body. Someone who is not yet aware of their affliction turns into an NPC while in animal form. Keep in mind that not all lycanthropic animal-forms are evil. The wereboar you are interested in, for instance, is neutral. This means that it would not go on random killing sprees, destroying everything in its path. But it is still basically a wild animal. Easily startled, protective, etc. Especially boars are pretty territorial, so while a wereboar might not go out of its way to murder people, it would certainly attack all that it sees as intruders. And what happens when someone no longer belongs to their original species? Would a wereboar still see its fellow villagers are 'people that share this territory with me'? Most likely not. I assume that a wereboar will not realise that HE was the one that changed, and instead assumes that the other villagers are intruding upon the territory of him and a few 'other boars' (the other villagers).
Eventually, given enough time, a lycanthrope is fated to adopt the same allignment as their beast form. This does not mean 'the same philosophy' of course, but it will still change a person a lot. A lawful good paladin who becomes chaotic evil might suddenly see the merit in his Werewolf curse, and wish to keep it to make up for his lost paladin-powers (since he is no longer lawful good.) An evil crime-loa\rd may suddenly start working within the bounderies of the law upon becoming lawful good because of his were-bearness. Etc. But, as everything, it all depends on the afflicted character.