They may be, but that is not why there are laws against them. There are laws against rape, murder, and theft because those things violate the rights of others.
Let's see what early American law said about the reason for having laws. This is taken from an 1815 PA Supreme Court Decision.
This court is...invested with power to punish not only open violations of decency and morality, but also whatever secretly tends to undermine the principles of society...
Whatever tends to the destruction of morality, in general, may be punishable criminally. Crimes are public offenses, not because they are perpetrated publically, but because their effect is to injure the public. Buglary, though done in secret, is a public offense; and secretly destroying fences is indictable.
Hence it follows, that an offense may be punishable, if in it's nature and by it's example, it tends to the corruption or morals; although it not be committed in public.
Although every immoral act, such as lying, ect... is not indictable, yet where the offense charged is destructive of morality in general...it is punishable at common law. The destruction of morality renders the power of government invalid...
No man is permitted to corrupt the morals of the people, secret poision cannot be thus desseminated.