Is Osaka-ben really that bad?

I know it's a little harsh, but is it really that bad when you are talking to a non-Osakan?
A guy (who's non-Osakan) said when he knew that I'm interested in it's like "threatening the other party".
and another one said (Osakan)
"Go for it!".
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What do you think?

Are you asking if it is bad to speak in Osaka-ben when speaking to non-Osakans? Of course not, as long as it's naturally coming from you. Look at all the manzai guys on TV. It would be "odd" however, if you use fake Osaka-ben without not really knowing the dialect.

If you live in Osaka, you would naturally pick up Osaka dialect. There are some people who simply do not like other dialects. Just be aware that if it doesn't come naturally, you might sound mocking.

Speaking as a foreigner who has been living in Osaka a couple of years, if you live here and pick it up the same way you pick everything else up, it's fine- my Japanese has been very influenced by Osaka-ben. No one has ever had a problem with it, though I do sometimes get amused smiles and gentle teasing from Kanto friends when I go to Tokyo and say something without realizing the phrasing/intonation are Osaka-specific. But if you make Japanese friends in Osaka, they'll probably all use Osaka-ben, and you can't help but pick it up.

OTOH, a lot of foreigners who come to Osaka specifically try and study Osaka-ben without learning correct grammar etc., just because they think it sounds fun or cool, and they usually end up sounding rough or stupid because they use it incorrectly or just spit out phrases memorized from a book.

It also goes without saying there are some workplaces where Osaka-ben would be a don't, i think try to use standard Japanese at work is better advice than don't use Osaka-ben at all :)

I don't know where Ojanne-the original poster-come from but in most, if not all, countries there is a standard official language (in many countries it is often the language spoken by the upper class in the capital) then there are regional languages and dialects (the 2 are different things).
For example in France the "proper" French comes from the Parisian region and has been codified by the upper classes. BUT working class Parisians speak a different French. (different in accent and vocabulary it is a dialect and there is also a Parisian slang). Each region of France speaks either a French that is a mix of standard French and the old non-French native language that was commonly spoken in that region until WW I. OR a dialect of French different from Parisian French, like Normand, Picard, Berrichon etc. Pretty much everybody knows how to switch to an average standard French when speaking to people from other regions but nowadays regional accents are OK, even on national TV.
This relates a bit to Osaka-ben as immigrants and their children end up speaking whatever French is spoken in the town they live in (as if they had lived there for generations) not the official French they hear on the national TV news.
You will find this mix of dialects and languages everywhere: in the UK, Italy, Spain, China.. even in young countries like the USA and Canada.
If the OP is seriously interested in Osaka-ben, more power to him. ALL languages and dialects have a value.

Just to add....

The standard Japanese is the one NHK anchors use. Others, including the one spoken in Tokyo, are all dialects. The truth is nobody talks standard Japanese in real life.

Standard Japanese (hyojungo) is indeed spoken in real life. As Vita suggested, in business scenes, it is expected to be used and you are taught the proper terms in your freshman study sessions.

The truth is, standard Japanese is quite often switched to dialects (including Tokyo dialect) once you go out for lunch or a drink in the evening :)

Nobody speaks standard Japanese Hyojyungo, like NHK, in casual conversation of daily life.
It is spoken in formal situations between persons who are not friends or family.