Practically the problem with this is that unless you know the right thing to do before hand then you can't determine the right thing to do. The hypocrite does one thing and instructs you not to do that thing (or to do another instead) - but by their actions they're showing, rightly or wrongly, that the thing they're counselling against is something they've chosen [to some extent] for themselves.
In the case of the meth addict you assume that they're being helpful because you assume (barring personal wisdom on the matter) that meth is bad, m'kay. But perhaps they just want to keep all the lovely, lovely meth for themselves??
If a person espouses a universal good - avoiding meth is good for everyone. Or if that person espouses a personal good without explaining why it doesn't apply to them - avoiding meth is good for you. But still that person acts opposite to that they espouse - eg take meth. Then they're acting contrary to what they state will be to their benefit.
You can't trust such a person. Either they act in ways that they know are detrimental or they are lying to you about the benefits available by following their actions.
So you can't trust a hypocrites testimony nor can you - without outside knowledge - learn what actions are best to take solely from their testimony.
Coming back to the case in hand. Is it wrong to copy someone's design? We can't tell if Apple Corp consider it wrong or right. All we know is that they're untrustworthy. Then they use legal process to punish someone for allegedly copying a design whilst on the other hand copying a design and show that they're willing to act to the detriment of others who follow their lead. It's kinda hypocrisy+plus: not only do we say not to do that which we do but we'll punish you for doing that which we do.
>narrow minded logic explained in the article, that cares not what is good for them to do, but if the guy that advocates it is "consistent" //
Whatever a hypocrite advocates is basically irrelevant. One should discard their testimony about the good of an action and use outside sources/testimony to establish independently the nature of any good that can be derived by following their instruction. A hypocrite though, as you appear to contend, would be a valid source of ideas just not a sound source of wisdom (ie take their idea but don't follow it without independently examining it).
tl;dr don't trust a hypocrite
Yes, this is where THINKING comes in.
First step, stop caring about anything specific about the person that gave you the advice, and only consider the advice.
Second step, try to think if it's good advice, in itself. If it is, follow it.
The guy being a hypocrite or not should not come into play at all. Neither should trust.
You should not follow some advice because you trust the guy who suggested it to you. You should follow it because you evaluated it.
In particular, if a person's behavior or circumstances conflict with the advice, it becomes important to evaluate why that conflict exists. Is the advice fundamentally sound and there's something wrong with the advice-giver, or is the problem with the advice itself? There may be some subtle implementation detail that you overlook in your theoretical "ignore the person" evaluation, which is actually a fatal flaw with the advice (for example, it may require an unrealistic amount of discipline to undertake.)
Likewise, if a person's advice and their behavior/circumstances match up, it's important to evaluate whether the advice is actually effective. Did this person see this result because of the advice, or because of something else? It's possible the advice is fundamentally sound; likewise, it's possible the advice is a mistaken conclusion based on coincidence. If the person giving the advice is known to be insightful, self-examining, etc. that suggests a greater likelihood of the advice being valuable.
If the person is a domain expert (or probably just 'more likely than you to know about it') and you are not and you have other reasons, past experience perhaps, then trusting their advice with little analysis (beyond eg 'was it a joke') is pragmatic. One can't analyse everything there is simply not enough time.
At some point you must trust others or suffer. It's about balance n'est ce pas?