As for the explanation, you will find it on the same link:
The understood subject of both the main clause (independent) and the participle clause (dependent) should be the same person(s) or thing(s).
Thanks, Ahmed. Since John121 (Welcome to the Grammar Exchange, John 121!) has quoted an explanation that is almost identical to that explanation, the problem seems to be that he can't understand the explanation. He wants to have the explanation explained to him.
Being a guy, *it is hard for him to understand her point of view.
Having heard this before, *her patience was wearing thin.
Being very rational, *speaking frankly was a very important to him.
Wounding like an arrow, *he sometimes hated to hear the truth.
Mentioned as constructive criticism,*there were no hard feelings.
Surely you can identify the main clause of each example, John121. In each example, the main clause is the part of the sentence which comes after the comma. The subject of the main clause is the subject of the sentence. The subject noun phrases are, respectively, "it," "her patience," "speaking frankly," "he," and "there."
Now let's look at the non-finite participial clauses which precede the main clauses. Each consists of a non-finite verb phrase, which forms a predicate. The predicate lacks an overt subject. Notice that we can't have sentences like "Is a guy," "Have heard this before," "Is very rational," "Mentioned as constructive criticism."
What is missing from such sentence fragments? They have no subject. In your examples, however, the non-finite correlates do have an implied subject. That subject is the subject of the main clause. The point that you need to understand is that the subject of the main clause needs to make sense as an implied subject of the participial clause.
In your examples, it does not make sense to construe the subject of the main clause as the implied subject of the participial clause. "It" cannot be a guy; it was not "her patience" that had heard this before; "speaking frankly" is not a rational entity; and "there" cannot be something that is mentioned as constructive criticism.
Each of the participial clauses, therefore, does not work. Each constitutes what is called a dangling modifier. Dangling modifiers do frequently occur in speech and writing, and some are worse than others. But speakers and writers should be on guard against them and try to rearrange sentences so that the modifiers do not dangle -- e.g.:
(1a) Being a guy, he has a hard time understanding her point of view.
(2a) Having heard this before, she had little patience to hear it again.
(3a) Being very rational, he thought it very important to speak frankly.
I have fixed the first three examples. The last two examples should be entirely rewritten. You can see that in each of the examples as I've revised them the participial clause does not dangle. The implied subject of "being a guy" is "he"; the implied subject of "having heard this before" is "she"; and the implied subject of "being very rational" is "he."
Do you understand now?