That is based on an incomplete understanding of the nature of rights. Rights, when understood as noncontradictory axioms, do not require conditions because they contain their limitations in their expression.
For example, property rights can be described thus: "All persons have the right to the full and exclusive use of their property." That statement imples that nobody has the right to use another person's property without his permission, so it is redundant to add "as long as they don't damage another person's property". Stating the redundant part can help to clarify, but it is not necessary to make the statement internally consistent.
The argument for arms is derived directly from the argument for the right to life: "All persons have the right to maintain and protect their lives." This position implies that whenever someone initiates force against another or threatens to do so, that other person has the right to repel that force or dispel that threat, as either would prevent him from maintaining his life. That in turn requires that a person be able to equip himself toward that defensive activity, as a prohibition against such equipment would constitute an intitiation of force, which is proscribed by the initial right to life. Therefore a prohibition against arms is an abridgement of the right to life.
Since a person has the right to dispel a threat against his life, a person exhibiting the intent and means to do violent harm against a non-aggressor may be justly prohibited from bearing arms (deprived of the means to do harm). This does not make the right "conditional", because it is implied by the original statement. And it does not justify the arbitrary restriction against "felons" owning guns, as many felons have never demonstrated the intent to harm another. Nor does it necessarily justify prohibiting arms from the mentally unsound, because not everyone who is mentally unsound is a threat to others or themselves.
As far as the freedom of speech goes, that is also subordinate to property rights. You don't have the right to say ANYTHING I don't like when you're in my house; if I say you can't say the word "tangerine", and you do, I can declare you a trespasser and kick you out. That might make me a jerk, but it would be within my rights. Likewise, you don't have the right to impede the fulfillment of a moviegoer's contract with the theater to enjoy a movie in peace and quiet. That is also an issue of property rights. If there were a theater that declared that movies may be subject to interruption by people yelling "fire" at any time, they could sell tickets with those conditions attatched, and you could yell "fire" to your heart's content without violating the rights of the theater or your fellow moviegoers.
The rights described in the constitution are not declarations of natural rights. Rather, they are prohibitions against the government infringing on natural rights which are already assumed to exist. And unfortunately, they are incomplete recognitions of natural rights, vaguely defined, and in some cases, contradictory.
