It is a truism that anyone who is tolerant is against intolerance. This truism will, however, turn into an apparent paradox if it is put this way: anyone who is tolerant is intolerant of intolerance. It seems that a tolerant person is necessarily intolerant in some respect, and this is supposed to be paradoxical.
I am not sure I understand why this is paradoxical. First of all, it is not clear that a tolerant person has to be tolerant of everything. Tolerance is a matter of degree. Perhaps we have to say that a tolerant person who is intolerant of intolerance is not completely or perfectly tolerant, but it is not paradoxical to say so. Secondly, we may distinguish between reasonable tolerance and unreasonable tolerance, and hold that tolerance of intolerance is unreasonable, and hence that it is all right for a tolerant person to be intolerant of intolerance.
In any case, I doubt that the truism that anyone who is tolerant is against intolerance is equivalent to the apparently paradoxical claim that anyone who is tolerant is intolerant of intolerance. To be tolerant of a view, a value, or an action, one does not have to accept it or agree with it; one only has to refrain from trying to suppress it or interfere with it. So it is possible for one to be against something and still be tolerant of it. I am, for example, against religion, but I am certainly tolerant of it.
The truism is thus not paradoxical, and the apparently paradoxical claim does not seem true. So, where is the paradox?