that Polish language sounds really angry and vulgar
That's the people, not the language... I think Polish sounds softer than Czech (for example)
The phonetic traits that make speakers sound angry in some languages (like guttural or tense sounds, tones) barely exist in Polish.
Post a link of someone speaking Polish that sounds angry and vulgar to you (independent of content).
Polish can sound a bit monotonous both because it is syllable timed (like Spanish or Italian) and the intonational spread (difference between high and low and soft and loud) is smaller than in some languages in Europe.