While the sentence "My points are true and constructive," is gramatically correct (going by parts of speech), it's awkward to read because "a point" (in the sense of the essential theme of a speech, as opposed to a tapering extremity) is not usually modified by the word "true" in the sense of "holding veracity" (as opposed to "actual.")
Were you to use that particular lexcon in another example (e.g. "I found his true points to be constructive.") you will note that "true" begins to take on the meaning of "actual," rather than "valid," which is no doubt what you meant to convey in your sentence above.
You should be more careful in your word choices in the future to make sure the true point of what you are trying to convey shows through in you criticism, which is not only constructive but also much admired both on this site and throughout the intellectual community of the Internet.
Thank you.